linux-kernel - Re: [PATCH v2] coccinelle: device_attr_show: Adapt to the latest Documentation/filesystems/sysfs.rst

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Date: Sat, 20 Jan 2024 22:20:26 +0100 (CET)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Li Zhijian <lizhijian@...itsu.com>
cc: linux-kernel@...r.kernel.org, Nicolas Palix <nicolas.palix@...g.fr>, 
    cocci@...ia.fr
Subject: Re: [PATCH v2] coccinelle: device_attr_show: Adapt to the latest
 Documentation/filesystems/sysfs.rst



On Fri, 19 Jan 2024, Li Zhijian wrote:

> Adapt description, warning message and MODE=patch according to the latest
> Documentation/filesystems/sysfs.rst:
> > show() should only use sysfs_emit() or sysfs_emit_at() when formatting
> > the value to be returned to user space.
>
> After this patch:
> When MODE=report,
>  $ make coccicheck COCCI=scripts/coccinelle/api/device_attr_show.cocci M=drivers/hid/hid-picolcd_core.c MODE=report
>  <...snip...>
>  drivers/hid/hid-picolcd_core.c:304:8-16: WARNING: please use sysfs_emit or sysfs_emit_at
>  drivers/hid/hid-picolcd_core.c:259:9-17: WARNING: please use sysfs_emit or sysfs_emit_at
>
> When MODE=patch,
>  $ make coccicheck COCCI=scripts/coccinelle/api/device_attr_show.cocci M=drivers/hid/hid-picolcd_core.c MODE=patch
>  <...snip...>
>  diff -u -p a/drivers/hid/hid-picolcd_core.c b/drivers/hid/hid-picolcd_core.c
>  --- a/drivers/hid/hid-picolcd_core.c
>  +++ b/drivers/hid/hid-picolcd_core.c
>  @@ -255,10 +255,12 @@ static ssize_t picolcd_operation_mode_sh
>   {
>          struct picolcd_data *data = dev_get_drvdata(dev);
>
>  -       if (data->status & PICOLCD_BOOTLOADER)
>  -               return snprintf(buf, PAGE_SIZE, "[bootloader] lcd\n");
>  -       else
>  -               return snprintf(buf, PAGE_SIZE, "bootloader [lcd]\n");
>  +       if (data->status & PICOLCD_BOOTLOADER) {
>  +               return sysfs_emit(buf, "[bootloader] lcd\n");
>  +       }
>  +       else {
>  +               return sysfs_emit(buf, "bootloader [lcd]\n");
>  +       }
>   }
>
>   static ssize_t picolcd_operation_mode_store(struct device *dev,
>  @@ -301,7 +303,7 @@ static ssize_t picolcd_operation_mode_de
>   {
>          struct picolcd_data *data = dev_get_drvdata(dev);
>
>  -       return snprintf(buf, PAGE_SIZE, "hello world\n");
>  +       return sysfs_emit(buf, "hello world\n");
>   }
>
>   static ssize_t picolcd_operation_mode_delay_store(struct device *dev,
>
> CC: Julia Lawall <Julia.Lawall@...ia.fr>
> CC: Nicolas Palix <nicolas.palix@...g.fr>
> CC: cocci@...ia.fr
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> ---
> V2:
> - changed title from coccinelle: device_attr_show.cocci: update description and warning message
> - Fix MODE=patch
> - Extract patch from the patch set[1] so that maintainer can accept it separately.

Applied.

I subsequently simplified the patch case to contain the following:

-              snprintf(BUF, SZ, FORMAT
+              sysfs_emit(BUF, FORMAT
                               ,...);

This also works for the case where there are only three arguments.
It has the benefit that the change is recognized as a line replacement, so
no extra {} are added when the call is in an if branch.

julia



> [1] https://lore.kernel.org/lkml/20240116041129.3937800-1-lizhijian@fujitsu.com/
> ---
>  scripts/coccinelle/api/device_attr_show.cocci | 22 +++++++++++--------
>  1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/scripts/coccinelle/api/device_attr_show.cocci b/scripts/coccinelle/api/device_attr_show.cocci
> index a28dc061653a..634514937e63 100644
> --- a/scripts/coccinelle/api/device_attr_show.cocci
> +++ b/scripts/coccinelle/api/device_attr_show.cocci
> @@ -1,10 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  ///
>  /// From Documentation/filesystems/sysfs.rst:
> -///  show() must not use snprintf() when formatting the value to be
> -///  returned to user space. If you can guarantee that an overflow
> -///  will never happen you can use sprintf() otherwise you must use
> -///  scnprintf().
> +///  show() should only use sysfs_emit() or sysfs_emit_at() when formatting
> +///  the value to be returned to user space.
>  ///
>  // Confidence: High
>  // Copyright: (C) 2020 Denis Efremov ISPRAS
> @@ -30,15 +28,21 @@ ssize_t show(struct device *dev, struct device_attribute *attr, char *buf)
>
>  @rp depends on patch@
>  identifier show, dev, attr, buf;
> +expression BUF, SZ, FORMAT, STR;
>  @@
>
>  ssize_t show(struct device *dev, struct device_attribute *attr, char *buf)
>  {
>  	<...
> +(
>  	return
> --		snprintf
> -+		scnprintf
> -			(...);
> +-		snprintf(BUF, SZ, FORMAT, STR);
> ++		sysfs_emit(BUF, FORMAT, STR);
> +|
> +	return
> +-		snprintf(BUF, SZ, STR);
> ++		sysfs_emit(BUF, STR);
> +)
>  	...>
>  }
>
> @@ -46,10 +50,10 @@ ssize_t show(struct device *dev, struct device_attribute *attr, char *buf)
>  p << r.p;
>  @@
>
> -coccilib.report.print_report(p[0], "WARNING: use scnprintf or sprintf")
> +coccilib.report.print_report(p[0], "WARNING: please use sysfs_emit or sysfs_emit_at")
>
>  @script: python depends on org@
>  p << r.p;
>  @@
>
> -coccilib.org.print_todo(p[0], "WARNING: use scnprintf or sprintf")
> +coccilib.org.print_todo(p[0], "WARNING: please use sysfs_emit or sysfs_emit_at")
> --
> 2.29.2
>
>