Re: [PATCH RESEND v4 2/2] ALSA: control: add ioctl to retrieve full card components

[Jaroslav Kysela <perex@perex.cz>]

On 6/25/26 14:07, Maciej Strozek wrote:

...

> +struct snd_ctl_card_bytes {
> +	unsigned int type;		/* SND_CTL_CARD_BTYPE_* */
> +	unsigned int data_allocated;	/* size of @data buffer in bytes */
> +	unsigned int data_len;		/* in/out: actual data length in bytes */
> +	unsigned char *data;		/* user buffer */

I know that I suggested to add code to the compat layer. But it seems that new 
UAPIs are using just '__u64 data' here with padding to 8 bytes (I would add 
new reserved field and perhaps we may use force `__u32' type for all other 
fields). The code in kernel sound translate the u64 data to pointer using 
u64_to_user_ptr() function.

So like:

struct snd_ctl_card_bytes {
       __u32 type;
       __u32 data_allocated;
       __u32 data_len;
       __u32 reserved;   /* explicit pad */
       __u64 data;       /* pointer as __u64 */
};

> +static int snd_ctl_card_bytes(struct snd_card *card,
> +			      struct snd_ctl_card_bytes *info,
> +			      unsigned int __user *data_len_out)
> +{
> +	unsigned int data_len;
> +
> +	switch (info->type) {
> +	case SND_CTL_CARD_BTYPE_COMPONENTS:
> +		scoped_guard(rwsem_read, &snd_ioctl_rwsem) {
> +			data_len = strlen(card->components) + 1;

The field card->components may be NULL here, also fix other uses like in 
snd_ctl_card_info().

		Thank you,
			Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat