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On Wed, Oct 13, 2021 at 12:53:14AM +0800, Yunhao Tian wrote:
> From: Yunhao Tian <t123yh.xyz@xxxxxxxxx>
>
> Currently, an array is used to contain all snd_kcontrol_new objects
> of the audio gadget. This is unnecessary and possibly prone to an
> (unlikely happen) race condition between the assignment of name
> and call of snd_ctl_new1 if two audio gadget is being set up simutaneously.
> This patch removes the global snd_kcontrol_new array and initialize
> individual snd_kcontrol_new object when it's being used.
>
> Signed-off-by: Yunhao Tian <t123yh.xyz@xxxxxxxxx>
> ---
> drivers/usb/gadget/function/u_audio.c | 65 +++++++++++----------------
> 1 file changed, 25 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
> index c5f39998c653..1f4226d75dd8 100644
> --- a/drivers/usb/gadget/function/u_audio.c
> +++ b/drivers/usb/gadget/function/u_audio.c
> @@ -27,12 +27,6 @@
> #define PRD_SIZE_MAX PAGE_SIZE
> #define MIN_PERIODS 4
>
> -enum {
> - UAC_FBACK_CTRL,
> - UAC_MUTE_CTRL,
> - UAC_VOLUME_CTRL,
> -};
> -
> /* Runtime data params for one stream */
> struct uac_rtd_params {
> struct snd_uac_chip *uac; /* parent chip */
> @@ -914,31 +908,6 @@ static int u_audio_volume_put(struct snd_kcontrol *kcontrol,
> return change;
> }
>
> -
> -static struct snd_kcontrol_new u_audio_controls[] = {
> - [UAC_FBACK_CTRL] {
> - .iface = SNDRV_CTL_ELEM_IFACE_PCM,
> - .name = "Capture Pitch 1000000",
> - .info = u_audio_pitch_info,
> - .get = u_audio_pitch_get,
> - .put = u_audio_pitch_put,
> - },
> - [UAC_MUTE_CTRL] {
> - .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> - .name = "", /* will be filled later */
> - .info = u_audio_mute_info,
> - .get = u_audio_mute_get,
> - .put = u_audio_mute_put,
> - },
> - [UAC_VOLUME_CTRL] {
> - .iface = SNDRV_CTL_ELEM_IFACE_MIXER,
> - .name = "", /* will be filled later */
> - .info = u_audio_volume_info,
> - .get = u_audio_volume_get,
> - .put = u_audio_volume_put,
> - },
> -};
> -
> int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
> const char *card_name)
> {
> @@ -946,6 +915,7 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
> struct snd_card *card;
> struct snd_pcm *pcm;
> struct snd_kcontrol *kctl;
> + struct snd_kcontrol_new kctl_new;
> struct uac_params *params;
> int p_chmask, c_chmask;
> int i, err;
> @@ -1043,8 +1013,14 @@ int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
> strscpy(card->mixername, card_name, sizeof(card->driver));
>
> if (c_chmask && g_audio->in_ep_fback) {
> - kctl = snd_ctl_new1(&u_audio_controls[UAC_FBACK_CTRL],
> - &uac->c_prm);
> + kctl_new = (struct snd_kcontrol_new) {
> + .iface = SNDRV_CTL_ELEM_IFACE_PCM,
> + .name = "Capture Pitch 1000000",
> + .info = u_audio_pitch_info,
> + .get = u_audio_pitch_get,
> + .put = u_audio_pitch_put,
> + };
> + kctl = snd_ctl_new1(&kctl_new, &uac->c_prm);
Did you test this code? Now this data is on the stack and will be
removed later on, while the original code's data will persist after this
function returns.
Are you sure this is ok?
thanks,
greg k-h
