![Peter Zijlstra](/assets/img/avatar_default.png)
Since we need to change the implementation, stop exposing internals. Provide kref_read() to read the current reference count; typically used for debug messages. Kills two anti-patterns: atomic_read(&kref->refcount) kref->refcount.counter Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
628 lines
17 KiB
C
628 lines
17 KiB
C
/*
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* comedi_buf.c
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*
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* COMEDI - Linux Control and Measurement Device Interface
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* Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
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* Copyright (C) 2002 Frank Mori Hess <fmhess@users.sourceforge.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/vmalloc.h>
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#include <linux/slab.h>
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#include "comedidev.h"
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#include "comedi_internal.h"
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#ifdef PAGE_KERNEL_NOCACHE
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#define COMEDI_PAGE_PROTECTION PAGE_KERNEL_NOCACHE
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#else
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#define COMEDI_PAGE_PROTECTION PAGE_KERNEL
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#endif
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static void comedi_buf_map_kref_release(struct kref *kref)
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{
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struct comedi_buf_map *bm =
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container_of(kref, struct comedi_buf_map, refcount);
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struct comedi_buf_page *buf;
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unsigned int i;
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if (bm->page_list) {
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for (i = 0; i < bm->n_pages; i++) {
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buf = &bm->page_list[i];
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clear_bit(PG_reserved,
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&(virt_to_page(buf->virt_addr)->flags));
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if (bm->dma_dir != DMA_NONE) {
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#ifdef CONFIG_HAS_DMA
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dma_free_coherent(bm->dma_hw_dev,
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PAGE_SIZE,
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buf->virt_addr,
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buf->dma_addr);
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#endif
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} else {
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free_page((unsigned long)buf->virt_addr);
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}
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}
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vfree(bm->page_list);
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}
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if (bm->dma_dir != DMA_NONE)
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put_device(bm->dma_hw_dev);
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kfree(bm);
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}
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static void __comedi_buf_free(struct comedi_device *dev,
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struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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struct comedi_buf_map *bm;
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unsigned long flags;
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if (async->prealloc_buf) {
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vunmap(async->prealloc_buf);
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async->prealloc_buf = NULL;
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async->prealloc_bufsz = 0;
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}
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spin_lock_irqsave(&s->spin_lock, flags);
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bm = async->buf_map;
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async->buf_map = NULL;
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spin_unlock_irqrestore(&s->spin_lock, flags);
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comedi_buf_map_put(bm);
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}
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static void __comedi_buf_alloc(struct comedi_device *dev,
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struct comedi_subdevice *s,
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unsigned int n_pages)
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{
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struct comedi_async *async = s->async;
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struct page **pages = NULL;
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struct comedi_buf_map *bm;
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struct comedi_buf_page *buf;
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unsigned long flags;
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unsigned int i;
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if (!IS_ENABLED(CONFIG_HAS_DMA) && s->async_dma_dir != DMA_NONE) {
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dev_err(dev->class_dev,
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"dma buffer allocation not supported\n");
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return;
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}
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bm = kzalloc(sizeof(*async->buf_map), GFP_KERNEL);
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if (!bm)
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return;
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kref_init(&bm->refcount);
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spin_lock_irqsave(&s->spin_lock, flags);
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async->buf_map = bm;
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spin_unlock_irqrestore(&s->spin_lock, flags);
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bm->dma_dir = s->async_dma_dir;
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if (bm->dma_dir != DMA_NONE)
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/* Need ref to hardware device to free buffer later. */
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bm->dma_hw_dev = get_device(dev->hw_dev);
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bm->page_list = vzalloc(sizeof(*buf) * n_pages);
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if (bm->page_list)
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pages = vmalloc(sizeof(struct page *) * n_pages);
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if (!pages)
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return;
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for (i = 0; i < n_pages; i++) {
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buf = &bm->page_list[i];
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if (bm->dma_dir != DMA_NONE)
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#ifdef CONFIG_HAS_DMA
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buf->virt_addr = dma_alloc_coherent(bm->dma_hw_dev,
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PAGE_SIZE,
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&buf->dma_addr,
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GFP_KERNEL |
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__GFP_COMP);
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#else
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break;
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#endif
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else
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buf->virt_addr = (void *)get_zeroed_page(GFP_KERNEL);
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if (!buf->virt_addr)
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break;
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set_bit(PG_reserved, &(virt_to_page(buf->virt_addr)->flags));
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pages[i] = virt_to_page(buf->virt_addr);
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}
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spin_lock_irqsave(&s->spin_lock, flags);
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bm->n_pages = i;
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spin_unlock_irqrestore(&s->spin_lock, flags);
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/* vmap the prealloc_buf if all the pages were allocated */
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if (i == n_pages)
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async->prealloc_buf = vmap(pages, n_pages, VM_MAP,
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COMEDI_PAGE_PROTECTION);
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vfree(pages);
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}
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void comedi_buf_map_get(struct comedi_buf_map *bm)
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{
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if (bm)
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kref_get(&bm->refcount);
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}
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int comedi_buf_map_put(struct comedi_buf_map *bm)
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{
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if (bm)
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return kref_put(&bm->refcount, comedi_buf_map_kref_release);
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return 1;
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}
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/* returns s->async->buf_map and increments its kref refcount */
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struct comedi_buf_map *
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comedi_buf_map_from_subdev_get(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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struct comedi_buf_map *bm = NULL;
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unsigned long flags;
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if (!async)
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return NULL;
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spin_lock_irqsave(&s->spin_lock, flags);
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bm = async->buf_map;
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/* only want it if buffer pages allocated */
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if (bm && bm->n_pages)
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comedi_buf_map_get(bm);
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else
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bm = NULL;
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spin_unlock_irqrestore(&s->spin_lock, flags);
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return bm;
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}
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bool comedi_buf_is_mmapped(struct comedi_subdevice *s)
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{
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struct comedi_buf_map *bm = s->async->buf_map;
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return bm && (kref_read(&bm->refcount) > 1);
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}
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int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
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unsigned long new_size)
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{
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struct comedi_async *async = s->async;
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/* Round up new_size to multiple of PAGE_SIZE */
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new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;
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/* if no change is required, do nothing */
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if (async->prealloc_buf && async->prealloc_bufsz == new_size)
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return 0;
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/* deallocate old buffer */
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__comedi_buf_free(dev, s);
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/* allocate new buffer */
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if (new_size) {
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unsigned int n_pages = new_size >> PAGE_SHIFT;
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__comedi_buf_alloc(dev, s, n_pages);
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if (!async->prealloc_buf) {
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/* allocation failed */
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__comedi_buf_free(dev, s);
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return -ENOMEM;
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}
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}
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async->prealloc_bufsz = new_size;
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return 0;
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}
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void comedi_buf_reset(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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async->buf_write_alloc_count = 0;
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async->buf_write_count = 0;
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async->buf_read_alloc_count = 0;
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async->buf_read_count = 0;
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async->buf_write_ptr = 0;
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async->buf_read_ptr = 0;
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async->cur_chan = 0;
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async->scans_done = 0;
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async->scan_progress = 0;
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async->munge_chan = 0;
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async->munge_count = 0;
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async->munge_ptr = 0;
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async->events = 0;
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}
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static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
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return free_end - async->buf_write_alloc_count;
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}
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unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
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return free_end - async->buf_write_count;
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}
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/**
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* comedi_buf_write_alloc() - Reserve buffer space for writing
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* @s: COMEDI subdevice.
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* @nbytes: Maximum space to reserve in bytes.
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*
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* Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition
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* data buffer associated with the subdevice. The amount reserved is limited
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* by the space available.
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*
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* Return: The amount of space reserved in bytes.
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*/
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unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
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unsigned int nbytes)
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{
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struct comedi_async *async = s->async;
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unsigned int unalloc = comedi_buf_write_n_unalloc(s);
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if (nbytes > unalloc)
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nbytes = unalloc;
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async->buf_write_alloc_count += nbytes;
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/*
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* ensure the async buffer 'counts' are read and updated
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* before we write data to the write-alloc'ed buffer space
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*/
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smp_mb();
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return nbytes;
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}
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EXPORT_SYMBOL_GPL(comedi_buf_write_alloc);
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/*
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* munging is applied to data by core as it passes between user
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* and kernel space
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*/
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static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
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unsigned int num_bytes)
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{
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struct comedi_async *async = s->async;
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unsigned int count = 0;
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const unsigned int num_sample_bytes = comedi_bytes_per_sample(s);
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if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) {
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async->munge_count += num_bytes;
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count = num_bytes;
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} else {
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/* don't munge partial samples */
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num_bytes -= num_bytes % num_sample_bytes;
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while (count < num_bytes) {
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int block_size = num_bytes - count;
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unsigned int buf_end;
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buf_end = async->prealloc_bufsz - async->munge_ptr;
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if (block_size > buf_end)
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block_size = buf_end;
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s->munge(s->device, s,
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async->prealloc_buf + async->munge_ptr,
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block_size, async->munge_chan);
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/*
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* ensure data is munged in buffer before the
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* async buffer munge_count is incremented
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*/
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smp_wmb();
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async->munge_chan += block_size / num_sample_bytes;
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async->munge_chan %= async->cmd.chanlist_len;
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async->munge_count += block_size;
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async->munge_ptr += block_size;
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async->munge_ptr %= async->prealloc_bufsz;
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count += block_size;
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}
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}
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return count;
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}
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unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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return async->buf_write_alloc_count - async->buf_write_count;
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}
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/**
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* comedi_buf_write_free() - Free buffer space after it is written
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* @s: COMEDI subdevice.
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* @nbytes: Maximum space to free in bytes.
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*
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* Free up to @nbytes bytes of space previously reserved for writing in the
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* COMEDI acquisition data buffer associated with the subdevice. The amount of
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* space freed is limited to the amount that was reserved. The freed space is
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* assumed to have been filled with sample data by the writer.
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*
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* If the samples in the freed space need to be "munged", do so here. The
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* freed space becomes available for allocation by the reader.
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*
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* Return: The amount of space freed in bytes.
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*/
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unsigned int comedi_buf_write_free(struct comedi_subdevice *s,
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unsigned int nbytes)
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{
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struct comedi_async *async = s->async;
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unsigned int allocated = comedi_buf_write_n_allocated(s);
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if (nbytes > allocated)
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nbytes = allocated;
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async->buf_write_count += nbytes;
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async->buf_write_ptr += nbytes;
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comedi_buf_munge(s, async->buf_write_count - async->munge_count);
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if (async->buf_write_ptr >= async->prealloc_bufsz)
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async->buf_write_ptr %= async->prealloc_bufsz;
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return nbytes;
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}
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EXPORT_SYMBOL_GPL(comedi_buf_write_free);
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/**
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* comedi_buf_read_n_available() - Determine amount of readable buffer space
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* @s: COMEDI subdevice.
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*
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* Determine the amount of readable buffer space in the COMEDI acquisition data
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* buffer associated with the subdevice. The readable buffer space is that
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* which has been freed by the writer and "munged" to the sample data format
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* expected by COMEDI if necessary.
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*
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* Return: The amount of readable buffer space.
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*/
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unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s)
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{
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struct comedi_async *async = s->async;
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unsigned int num_bytes;
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if (!async)
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return 0;
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num_bytes = async->munge_count - async->buf_read_count;
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/*
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* ensure the async buffer 'counts' are read before we
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* attempt to read data from the buffer
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*/
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smp_rmb();
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return num_bytes;
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}
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EXPORT_SYMBOL_GPL(comedi_buf_read_n_available);
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/**
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* comedi_buf_read_alloc() - Reserve buffer space for reading
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* @s: COMEDI subdevice.
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* @nbytes: Maximum space to reserve in bytes.
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*
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* Reserve up to @nbytes bytes of previously written and "munged" buffer space
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* for reading in the COMEDI acquisition data buffer associated with the
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* subdevice. The amount reserved is limited to the space available. The
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* reader can read from the reserved space and then free it. A reader is also
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* allowed to read from the space before reserving it as long as it determines
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* the amount of readable data available, but the space needs to be marked as
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* reserved before it can be freed.
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*
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* Return: The amount of space reserved in bytes.
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*/
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unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s,
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unsigned int nbytes)
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{
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struct comedi_async *async = s->async;
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unsigned int available;
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available = async->munge_count - async->buf_read_alloc_count;
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if (nbytes > available)
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nbytes = available;
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async->buf_read_alloc_count += nbytes;
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/*
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* ensure the async buffer 'counts' are read before we
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* attempt to read data from the read-alloc'ed buffer space
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*/
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smp_rmb();
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return nbytes;
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}
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EXPORT_SYMBOL_GPL(comedi_buf_read_alloc);
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static unsigned int comedi_buf_read_n_allocated(struct comedi_async *async)
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{
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return async->buf_read_alloc_count - async->buf_read_count;
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}
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/**
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* comedi_buf_read_free() - Free buffer space after it has been read
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* @s: COMEDI subdevice.
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* @nbytes: Maximum space to free in bytes.
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*
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* Free up to @nbytes bytes of buffer space previously reserved for reading in
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* the COMEDI acquisition data buffer associated with the subdevice. The
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* amount of space freed is limited to the amount that was reserved.
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*
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* The freed space becomes available for allocation by the writer.
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*
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* Return: The amount of space freed in bytes.
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*/
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unsigned int comedi_buf_read_free(struct comedi_subdevice *s,
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unsigned int nbytes)
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{
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struct comedi_async *async = s->async;
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unsigned int allocated;
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/*
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* ensure data has been read out of buffer before
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* the async read count is incremented
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*/
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smp_mb();
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allocated = comedi_buf_read_n_allocated(async);
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if (nbytes > allocated)
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nbytes = allocated;
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async->buf_read_count += nbytes;
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async->buf_read_ptr += nbytes;
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async->buf_read_ptr %= async->prealloc_bufsz;
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return nbytes;
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}
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EXPORT_SYMBOL_GPL(comedi_buf_read_free);
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static void comedi_buf_memcpy_to(struct comedi_subdevice *s,
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const void *data, unsigned int num_bytes)
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{
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struct comedi_async *async = s->async;
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unsigned int write_ptr = async->buf_write_ptr;
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while (num_bytes) {
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unsigned int block_size;
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if (write_ptr + num_bytes > async->prealloc_bufsz)
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block_size = async->prealloc_bufsz - write_ptr;
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else
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block_size = num_bytes;
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memcpy(async->prealloc_buf + write_ptr, data, block_size);
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data += block_size;
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num_bytes -= block_size;
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write_ptr = 0;
|
|
}
|
|
}
|
|
|
|
static void comedi_buf_memcpy_from(struct comedi_subdevice *s,
|
|
void *dest, unsigned int nbytes)
|
|
{
|
|
void *src;
|
|
struct comedi_async *async = s->async;
|
|
unsigned int read_ptr = async->buf_read_ptr;
|
|
|
|
while (nbytes) {
|
|
unsigned int block_size;
|
|
|
|
src = async->prealloc_buf + read_ptr;
|
|
|
|
if (nbytes >= async->prealloc_bufsz - read_ptr)
|
|
block_size = async->prealloc_bufsz - read_ptr;
|
|
else
|
|
block_size = nbytes;
|
|
|
|
memcpy(dest, src, block_size);
|
|
nbytes -= block_size;
|
|
dest += block_size;
|
|
read_ptr = 0;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* comedi_buf_write_samples() - Write sample data to COMEDI buffer
|
|
* @s: COMEDI subdevice.
|
|
* @data: Pointer to source samples.
|
|
* @nsamples: Number of samples to write.
|
|
*
|
|
* Write up to @nsamples samples to the COMEDI acquisition data buffer
|
|
* associated with the subdevice, mark it as written and update the
|
|
* acquisition scan progress. If there is not enough room for the specified
|
|
* number of samples, the number of samples written is limited to the number
|
|
* that will fit and the %COMEDI_CB_OVERFLOW event flag is set to cause the
|
|
* acquisition to terminate with an overrun error. Set the %COMEDI_CB_BLOCK
|
|
* event flag if any samples are written to cause waiting tasks to be woken
|
|
* when the event flags are processed.
|
|
*
|
|
* Return: The amount of data written in bytes.
|
|
*/
|
|
unsigned int comedi_buf_write_samples(struct comedi_subdevice *s,
|
|
const void *data, unsigned int nsamples)
|
|
{
|
|
unsigned int max_samples;
|
|
unsigned int nbytes;
|
|
|
|
/*
|
|
* Make sure there is enough room in the buffer for all the samples.
|
|
* If not, clamp the nsamples to the number that will fit, flag the
|
|
* buffer overrun and add the samples that fit.
|
|
*/
|
|
max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s));
|
|
if (nsamples > max_samples) {
|
|
dev_warn(s->device->class_dev, "buffer overrun\n");
|
|
s->async->events |= COMEDI_CB_OVERFLOW;
|
|
nsamples = max_samples;
|
|
}
|
|
|
|
if (nsamples == 0)
|
|
return 0;
|
|
|
|
nbytes = comedi_buf_write_alloc(s,
|
|
comedi_samples_to_bytes(s, nsamples));
|
|
comedi_buf_memcpy_to(s, data, nbytes);
|
|
comedi_buf_write_free(s, nbytes);
|
|
comedi_inc_scan_progress(s, nbytes);
|
|
s->async->events |= COMEDI_CB_BLOCK;
|
|
|
|
return nbytes;
|
|
}
|
|
EXPORT_SYMBOL_GPL(comedi_buf_write_samples);
|
|
|
|
/**
|
|
* comedi_buf_read_samples() - Read sample data from COMEDI buffer
|
|
* @s: COMEDI subdevice.
|
|
* @data: Pointer to destination.
|
|
* @nsamples: Maximum number of samples to read.
|
|
*
|
|
* Read up to @nsamples samples from the COMEDI acquisition data buffer
|
|
* associated with the subdevice, mark it as read and update the acquisition
|
|
* scan progress. Limit the number of samples read to the number available.
|
|
* Set the %COMEDI_CB_BLOCK event flag if any samples are read to cause waiting
|
|
* tasks to be woken when the event flags are processed.
|
|
*
|
|
* Return: The amount of data read in bytes.
|
|
*/
|
|
unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
|
|
void *data, unsigned int nsamples)
|
|
{
|
|
unsigned int max_samples;
|
|
unsigned int nbytes;
|
|
|
|
/* clamp nsamples to the number of full samples available */
|
|
max_samples = comedi_bytes_to_samples(s,
|
|
comedi_buf_read_n_available(s));
|
|
if (nsamples > max_samples)
|
|
nsamples = max_samples;
|
|
|
|
if (nsamples == 0)
|
|
return 0;
|
|
|
|
nbytes = comedi_buf_read_alloc(s,
|
|
comedi_samples_to_bytes(s, nsamples));
|
|
comedi_buf_memcpy_from(s, data, nbytes);
|
|
comedi_buf_read_free(s, nbytes);
|
|
comedi_inc_scan_progress(s, nbytes);
|
|
s->async->events |= COMEDI_CB_BLOCK;
|
|
|
|
return nbytes;
|
|
}
|
|
EXPORT_SYMBOL_GPL(comedi_buf_read_samples);
|