From 536e2e34bd002267384b0668ffff3f023003a830 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Fri, 18 Aug 2017 09:11:56 +0100 Subject: [PATCH] genirq/debugfs: Triggering of interrupts from userspace When developing new (and therefore buggy) interrupt related code, it can sometimes be useful to inject interrupts without having to rely on a device to actually generate them. This functionnality relies either on the irqchip driver to expose a irq_set_irqchip_state(IRQCHIP_STATE_PENDING) callback, or on the core code to be able to retrigger a (edge-only) interrupt. To use this feature: echo -n trigger > /sys/kernel/debug/irq/irqs/IRQNUM WARNING: This is DANGEROUS, and strictly a debug feature. Do not use it on a production system. Your HW is likely to catch fire, your data to be corrupted, and reporting this will make you look an even bigger fool than the idiot who wrote this patch. Signed-off-by: Marc Zyngier Signed-off-by: Thomas Gleixner Link: http://lkml.kernel.org/r/20170818081156.9264-1-marc.zyngier@arm.com --- kernel/irq/debugfs.c | 50 +++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 49 insertions(+), 1 deletion(-) diff --git a/kernel/irq/debugfs.c b/kernel/irq/debugfs.c index 4d384edc0c64..c3fdb36dec30 100644 --- a/kernel/irq/debugfs.c +++ b/kernel/irq/debugfs.c @@ -5,6 +5,7 @@ */ #include #include +#include #include "internals.h" @@ -171,8 +172,55 @@ static int irq_debug_open(struct inode *inode, struct file *file) return single_open(file, irq_debug_show, inode->i_private); } +static ssize_t irq_debug_write(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct irq_desc *desc = file_inode(file)->i_private; + char buf[8] = { 0, }; + size_t size; + + size = min(sizeof(buf) - 1, count); + if (copy_from_user(buf, user_buf, size)) + return -EFAULT; + + if (!strncmp(buf, "trigger", size)) { + unsigned long flags; + int err; + + /* Try the HW interface first */ + err = irq_set_irqchip_state(irq_desc_get_irq(desc), + IRQCHIP_STATE_PENDING, true); + if (!err) + return count; + + /* + * Otherwise, try to inject via the resend interface, + * which may or may not succeed. + */ + chip_bus_lock(desc); + raw_spin_lock_irqsave(&desc->lock, flags); + + if (irq_settings_is_level(desc)) { + /* Can't do level, sorry */ + err = -EINVAL; + } else { + desc->istate |= IRQS_PENDING; + check_irq_resend(desc); + err = 0; + } + + raw_spin_unlock_irqrestore(&desc->lock, flags); + chip_bus_sync_unlock(desc); + + return err ? err : count; + } + + return count; +} + static const struct file_operations dfs_irq_ops = { .open = irq_debug_open, + .write = irq_debug_write, .read = seq_read, .llseek = seq_lseek, .release = single_release, @@ -186,7 +234,7 @@ void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc) return; sprintf(name, "%d", irq); - desc->debugfs_file = debugfs_create_file(name, 0444, irq_dir, desc, + desc->debugfs_file = debugfs_create_file(name, 0644, irq_dir, desc, &dfs_irq_ops); }