[PATCH] ALSA: usb-audio: mixer: Remove temporary string use in parse_clock_source_unit

[PATCH] ALSA: usb-audio: mixer: Remove temporary string use in parse_clock_source_unit

[Peter Ujfalusi]

The kctl->id.name can be directly passed to snd_usb_copy_string_desc() and
if the string has been fetched the suffix can be appended with the
append_ctl_name() call.
The temporary name string becomes redundant and can be removed.

This change will also fixes the following compiler warning/error (W=1):

sound/usb/mixer.c: In function ‘parse_audio_unit’:
sound/usb/mixer.c:1972:29: error: ‘ Validity’ directive output may be truncated writing 9 bytes into a region of size between 1 and 44 [-Werror=format-truncation=]
 1972 |                          "%s Validity", name);
      |                             ^~~~~~~~~
In function ‘parse_clock_source_unit’,
    inlined from ‘parse_audio_unit’ at sound/usb/mixer.c:2892:10:
sound/usb/mixer.c:1971:17: note: ‘snprintf’ output between 10 and 53 bytes into a destination of size 44
 1971 |                 snprintf(kctl->id.name, sizeof(kctl->id.name),
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1972 |                          "%s Validity", name);
      |                          ~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

The warnings got brought to light by a recent patch upstream:
commit 6d4ab2e97dcf ("extrawarn: enable format and stringop overflow warnings in W=1")

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
---
 sound/usb/mixer.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 9105ec623120..985b1aea9cdc 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -1929,7 +1929,6 @@ static int parse_clock_source_unit(struct mixer_build *state, int unitid,
 	struct uac_clock_source_descriptor *hdr = _ftr;
 	struct usb_mixer_elem_info *cval;
 	struct snd_kcontrol *kctl;
-	char name[SNDRV_CTL_ELEM_ID_NAME_MAXLEN];
 	int ret;
 
 	if (state->mixer->protocol != UAC_VERSION_2)
@@ -1966,10 +1965,9 @@ static int parse_clock_source_unit(struct mixer_build *state, int unitid,
 
 	kctl->private_free = snd_usb_mixer_elem_free;
 	ret = snd_usb_copy_string_desc(state->chip, hdr->iClockSource,
-				       name, sizeof(name));
+				       kctl->id.name, sizeof(kctl->id.name));
 	if (ret > 0)
-		snprintf(kctl->id.name, sizeof(kctl->id.name),
-			 "%s Validity", name);
+		append_ctl_name(kctl, " Validity");
 	else
 		snprintf(kctl->id.name, sizeof(kctl->id.name),
 			 "Clock Source %d Validity", hdr->bClockID);
-- 
2.42.0

Re: [PATCH] ALSA: usb-audio: mixer: Remove temporary string use in parse_clock_source_unit

[Takashi Iwai]

On Wed, 13 Sep 2023 11:39:33 +0200,
Peter Ujfalusi wrote:
> 
> The kctl->id.name can be directly passed to snd_usb_copy_string_desc() and
> if the string has been fetched the suffix can be appended with the
> append_ctl_name() call.
> The temporary name string becomes redundant and can be removed.
> 
> This change will also fixes the following compiler warning/error (W=1):
> 
> sound/usb/mixer.c: In function ‘parse_audio_unit’:
> sound/usb/mixer.c:1972:29: error: ‘ Validity’ directive output may be truncated writing 9 bytes into a region of size between 1 and 44 [-Werror=format-truncation=]
>  1972 |                          "%s Validity", name);
>       |                             ^~~~~~~~~
> In function ‘parse_clock_source_unit’,
>     inlined from ‘parse_audio_unit’ at sound/usb/mixer.c:2892:10:
> sound/usb/mixer.c:1971:17: note: ‘snprintf’ output between 10 and 53 bytes into a destination of size 44
>  1971 |                 snprintf(kctl->id.name, sizeof(kctl->id.name),
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  1972 |                          "%s Validity", name);
>       |                          ~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> 
> The warnings got brought to light by a recent patch upstream:
> commit 6d4ab2e97dcf ("extrawarn: enable format and stringop overflow warnings in W=1")
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

Thanks, applied now.


Takashi