At Wed, 24 Aug 2011 08:26:47 +0200, Takashi Iwai wrote:
At Wed, 24 Aug 2011 14:17:57 +0800, Lu Guanqun wrote:
On Wed, Aug 24, 2011 at 02:06:34PM +0800, Takashi Iwai wrote:
At Wed, 24 Aug 2011 11:12:43 +0800, Lu Guanqun wrote:
I don't see how info's owner field relates to kcontrol's count field. It should assign to info's count instead.
Let's assume this scenario:
- user reads the control element from kernel (the owner field is set)
- user changes some values
- user issues 'SNDRV_CTL_IOCTL_ELEM_REPLACE' ioctl.
With the original code, 'kctl' here gets a large count number due to its non-empty owner field. Therefore it fails on subsequent call snd_ctl_new().
In IOCTL_ELEM_ADD and REPLACE, count and owner struct fields have different meanings from others. The count contains the array size, not the number of identical elements. And the owner contains the number of elements to be created. So, the current code is correct.
This sounds tricky...
in snd_ctl_elem_info(): info->owner = pid_vnr(vd->owner->pid); } else { info->owner = -1;
This is where owner of info get assigned, but it's not number of elements to be created.
The kcontrol.count field is never exposed to user-space.
I'm a bit unclear on this.
What we need is the documentation of this feature...
So my test case seems to be wrong, but how should I change it? Do I need to clear the owner field when user space application sends down the REPLACE ioctl?
Yes. Maybe it'd be better to define a new struct and use it in ADD/REPLACE ioctls so that user sees a clear difference. The struct will be identical except for renaming from owner to elem_count or such.
I mean a patch like below (untested).
Takashi
--- diff --git a/include/sound/asound.h b/include/sound/asound.h index 5d6074f..9f5f55d 100644 --- a/include/sound/asound.h +++ b/include/sound/asound.h @@ -813,6 +813,33 @@ struct snd_ctl_elem_info { unsigned char reserved[64-4*sizeof(unsigned short)]; };
+/* The struct used for ELEM_ADD and ELEM_REPLACE ioctls; + * This is is identical with snd_ctl_elem_info, but just owner field is + * different, keeping the number of elements to be created. + * The unused fields are stripped for simplicity. + */ +struct snd_ctl_elem_add_info { + struct snd_ctl_elem_id id; /* element ID */ + snd_ctl_elem_type_t type; /* value type */ + unsigned int access; /* value access (bitmask) */ + unsigned int count; /* count of values */ + __kernel_pid_t elem_count; /* # of elements to create (0=1) */ + union { + struct { + long min; /* R: minimum value */ + long max; /* R: maximum value */ + long step; /* R: step (0 variable) */ + } integer; + struct { + long long min; /* R: minimum value */ + long long max; /* R: maximum value */ + long long step; /* R: step (0 variable) */ + } integer64; + unsigned char reserved[128]; + } value; + unsigned char reserved[64]; +}; + struct snd_ctl_elem_value { struct snd_ctl_elem_id id; /* W: element ID */ unsigned int indirect: 1; /* W: indirect access - obsoleted */ @@ -854,8 +881,8 @@ struct snd_ctl_tlv { #define SNDRV_CTL_IOCTL_ELEM_LOCK _IOW('U', 0x14, struct snd_ctl_elem_id) #define SNDRV_CTL_IOCTL_ELEM_UNLOCK _IOW('U', 0x15, struct snd_ctl_elem_id) #define SNDRV_CTL_IOCTL_SUBSCRIBE_EVENTS _IOWR('U', 0x16, int) -#define SNDRV_CTL_IOCTL_ELEM_ADD _IOWR('U', 0x17, struct snd_ctl_elem_info) -#define SNDRV_CTL_IOCTL_ELEM_REPLACE _IOWR('U', 0x18, struct snd_ctl_elem_info) +#define SNDRV_CTL_IOCTL_ELEM_ADD _IOWR('U', 0x17, struct snd_ctl_elem_add_info) +#define SNDRV_CTL_IOCTL_ELEM_REPLACE _IOWR('U', 0x18, struct snd_ctl_elem_add_info) #define SNDRV_CTL_IOCTL_ELEM_REMOVE _IOWR('U', 0x19, struct snd_ctl_elem_id) #define SNDRV_CTL_IOCTL_TLV_READ _IOWR('U', 0x1a, struct snd_ctl_tlv) #define SNDRV_CTL_IOCTL_TLV_WRITE _IOWR('U', 0x1b, struct snd_ctl_tlv) diff --git a/sound/core/control.c b/sound/core/control.c index dc2a440..15c171d 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -1064,7 +1064,7 @@ static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol) }
static int snd_ctl_elem_add(struct snd_ctl_file *file, - struct snd_ctl_elem_info *info, int replace) + struct snd_ctl_elem_add_info *info, int replace) { struct snd_card *card = file->card; struct snd_kcontrol kctl, *_kctl; @@ -1099,7 +1099,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, if (err < 0) return err; memcpy(&kctl.id, &info->id, sizeof(info->id)); - kctl.count = info->owner ? info->owner : 1; + kctl.count = info->elem_count ? info->elem_count : 1; access |= SNDRV_CTL_ELEM_ACCESS_USER; kctl.info = snd_ctl_elem_user_info; if (access & SNDRV_CTL_ELEM_ACCESS_READ) @@ -1139,7 +1139,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, ue = kzalloc(sizeof(struct user_element) + private_size, GFP_KERNEL); if (ue == NULL) return -ENOMEM; - ue->info = *info; + memcpy(&ue->info, info, sizeof(*info)); ue->info.access = 0; ue->elem_data = (char *)ue + sizeof(*ue); ue->elem_data_size = private_size; @@ -1164,9 +1164,10 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, }
static int snd_ctl_elem_add_user(struct snd_ctl_file *file, - struct snd_ctl_elem_info __user *_info, int replace) + struct snd_ctl_elem_add_info __user *_info, + int replace) { - struct snd_ctl_elem_info info; + struct snd_ctl_elem_add_info info; if (copy_from_user(&info, _info, sizeof(info))) return -EFAULT; return snd_ctl_elem_add(file, &info, replace);