| Message ID | 20220920135435.15593-1-brgl@bgdev.pl |
|---|---|
| State | Superseded |
| Headers | show |
| Series | gpiolib: cdev: add fdinfo output for line request file descriptors | expand |
On Tue, Sep 20, 2022 at 08:19:25PM +0300, Andy Shevchenko wrote: > On Tue, Sep 20, 2022 at 03:54:35PM +0200, Bartosz Golaszewski wrote: ... > Also don't forget that sizes over PAGE_SIZE in sysfs sometimes problematic and > racy.(the commit 888be6067b97 ("ACPI: sysfs: Fix a buffer overrun problem with > description_show()") for the reference). This is not the commit I wanted to point to... But suddenly can't find easily the one I remembered happened in the kernel.
On Tue, Sep 20, 2022 at 10:35:25PM +0200, Bartosz Golaszewski wrote: > On Tue, Sep 20, 2022 at 7:19 PM Andy Shevchenko > <andriy.shevchenko@linux.intel.com> wrote: > > On Tue, Sep 20, 2022 at 03:54:35PM +0200, Bartosz Golaszewski wrote: ... > > > + seq_printf(out, "gpio-device:\t%s\n", dev_name(dev)); > > > + > > > + for (i = 0; i < lr->num_lines; i++) > > > + seq_printf(out, "gpio-line:\t%d\n", > > > + gpio_chip_hwgpio(lr->lines[i].desc)); > > > > Hmm... Not sure which variant is better (as for machine parsing and for human), > > but I was thinking of > > IMO it's pretty clear that the variant in this patch is easier for > machine parsing - one less tokenization. For human it's harder in my opinion... But okay. > > gpio-lines: 1,4,6, ... > > > > Also don't forget that sizes over PAGE_SIZE in sysfs sometimes problematic and > > racy.(the commit 888be6067b97 ("ACPI: sysfs: Fix a buffer overrun problem with > > description_show()") for the reference). > > In most systems PAGE_SIZE will be at least 4096 bytes. With this patch > a single "gpio-line:\t65535\n" is at most 17 bytes long x max 64 lines > = 1088 bytes. We're still way below the size where it would be > problematic. Okay, for now it's 64, but it will be problematic starting from ~300 requested lines. Also, in case we add something more, who knows?
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index f8041d4898d1..0f7b5562c410 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -1497,6 +1497,21 @@ static int linereq_release(struct inode *inode, struct file *file) return 0; } +#ifdef CONFIG_PROC_FS +static void linereq_show_fdinfo(struct seq_file *out, struct file *file) +{ + struct linereq *lr = file->private_data; + struct device *dev = &lr->gdev->dev; + u16 i; + + seq_printf(out, "gpio-device:\t%s\n", dev_name(dev)); + + for (i = 0; i < lr->num_lines; i++) + seq_printf(out, "gpio-line:\t%d\n", + gpio_chip_hwgpio(lr->lines[i].desc)); +} +#endif + static const struct file_operations line_fileops = { .release = linereq_release, .read = linereq_read, @@ -1507,6 +1522,9 @@ static const struct file_operations line_fileops = { #ifdef CONFIG_COMPAT .compat_ioctl = linereq_ioctl_compat, #endif +#ifdef CONFIG_PROC_FS + .show_fdinfo = linereq_show_fdinfo, +#endif }; static int linereq_create(struct gpio_device *gdev, void __user *ip)
Add fdinfo output for file descriptors created for user-space line requests in GPIO uAPI v2. The fdinfo file now contains the name of the GPIO device that is the "parent" of the request as well as offsets of the lines requested. This allows user-space to parse the /proc/$PID/fdinfo entries and deduct the PID of the process that requested a specific line. Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl> --- drivers/gpio/gpiolib-cdev.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)