| Message ID | 20240726074750.626671-4-ivan.orlov0322@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce userspace-driven ALSA timers | expand |
Le 26/07/2024 à 09:47, Ivan Orlov a écrit : > Implement two ioctl calls in order to support virtual userspace-driven > ALSA timers. > > The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the > snd_utimer_info struct as a parameter and returns a file descriptor of > a virtual timer. It also updates the `id` field of the snd_utimer_info > struct, which provides a unique identifier for the timer (basically, > the subdevice number which can be used when creating timer instances). > > This patch also introduces a tiny id allocator for the userspace-driven > timers, which guarantees that we don't have more than 128 of them in the > system. > > Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger > the virtual timer (and calls snd_timer_interrupt for the timer under > the hood), causing all of the timer instances binded to this timer to > execute their callbacks. > > The maximum amount of ticks available for the timer is 1 for the sake of > simplification of the userspace API. 'start', 'stop', 'open' and 'close' > callbacks for the userspace-driven timers are empty since we don't > really do any hardware initialization here. > > Suggested-by: Axel Holzinger <aholzinger@gmx.de> > Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> > --- Hi, ... > diff --git a/sound/core/Kconfig b/sound/core/Kconfig > index b970a1734647..3cf82641fc67 100644 > --- a/sound/core/Kconfig > +++ b/sound/core/Kconfig > @@ -251,6 +251,17 @@ config SND_JACK_INJECTION_DEBUG > Say Y if you are debugging via jack injection interface. > If unsure select "N". > > +config SND_UTIMER > + bool "Enable support for userspace-controlled virtual timers" > + depends on SND_TIMER > + help > + Say Y to enable the support of userspace-controlled timers. These > + timers are purely virtual, and they are supposed to be triggered > + from userspace. They could be quite useful when synchronizing the > + sound timing with userspace applications (for instance, when sending > + data through snd-aloop). > + Unneeded extra new line. > + > config SND_VMASTER > bool > ... > +static void snd_utimer_free(struct snd_utimer *utimer) > +{ > + snd_timer_free(utimer->timer); > + snd_utimer_put_id(utimer); Missing kfree(utimer->name); ? > + kfree(utimer); > +} ... > +static int snd_utimer_create(struct snd_utimer_info *utimer_info, > + struct snd_utimer **r_utimer) > +{ > + struct snd_utimer *utimer; > + struct snd_timer *timer; > + struct snd_timer_id tid; > + int utimer_id; > + int err = 0; > + char *timer_name; > + > + utimer = kzalloc(sizeof(*utimer), GFP_KERNEL); > + if (!utimer) > + return -ENOMEM; > + > + timer_name = kzalloc(SNDRV_UTIMER_NAME_LEN, GFP_KERNEL); kasprintf(GFP_KERNEL, "snd-utimer%d", utimer_id); ? and SNDRV_UTIMER_NAME_LEN becomes useless too. In snd_timer_new() it is copied in a char[64] anyway, and if utimer_id is small, we could even save a few bytes of memory. CJ > + if (!timer_name) { > + kfree(utimer); > + return -ENOMEM; > + } > + > + /* We hold the ioctl lock here so we won't get a race condition when allocating id */ > + utimer_id = snd_utimer_take_id(); > + if (utimer_id < 0) { > + err = utimer_id; > + goto err_take_id; > + } > + > + sprintf(timer_name, "snd-utimer%d", utimer_id); > + utimer->name = timer_name; > + utimer->id = utimer_id; ...
Le 26/07/2024 à 09:47, Ivan Orlov a écrit : > Implement two ioctl calls in order to support virtual userspace-driven > ALSA timers. > > The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the > snd_utimer_info struct as a parameter and returns a file descriptor of > a virtual timer. It also updates the `id` field of the snd_utimer_info > struct, which provides a unique identifier for the timer (basically, > the subdevice number which can be used when creating timer instances). > > This patch also introduces a tiny id allocator for the userspace-driven > timers, which guarantees that we don't have more than 128 of them in the > system. > > Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger > the virtual timer (and calls snd_timer_interrupt for the timer under > the hood), causing all of the timer instances binded to this timer to > execute their callbacks. > > The maximum amount of ticks available for the timer is 1 for the sake of > simplification of the userspace API. 'start', 'stop', 'open' and 'close' > callbacks for the userspace-driven timers are empty since we don't > really do any hardware initialization here. > > Suggested-by: Axel Holzinger <aholzinger@gmx.de> > Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> > --- ... > +#ifdef CONFIG_SND_UTIMER > +/* > + * Since userspace-driven timers are passed to userspace, we need to have an identifier > + * which will allow us to use them (basically, the subdevice number of udriven timer). > + * > + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to (SNDRV_UTIMERS_MAX_COUNT - 1). > + * When we take one of them, the corresponding entry in snd_utimer_ids becomes true. > + */ > +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; > + > +static void snd_utimer_put_id(struct snd_utimer *utimer) > +{ > + int timer_id = utimer->id; > + > + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); > + snd_utimer_ids[timer_id] = false; > +} > + > +static int snd_utimer_take_id(void) > +{ > + size_t i; > + > + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { > + if (!snd_utimer_ids[i]) { > + snd_utimer_ids[i] = true; > + return i; > + } > + } > + > + return -EBUSY; > +} Also the bitmap API could be useful here. CJ
On 7/28/24 07:52, Christophe JAILLET wrote: > Hi, > Hi Christophe, > ... > >> diff --git a/sound/core/Kconfig b/sound/core/Kconfig >> index b970a1734647..3cf82641fc67 100644 >> --- a/sound/core/Kconfig >> +++ b/sound/core/Kconfig >> @@ -251,6 +251,17 @@ config SND_JACK_INJECTION_DEBUG >> Say Y if you are debugging via jack injection interface. >> If unsure select "N". >> +config SND_UTIMER >> + bool "Enable support for userspace-controlled virtual timers" >> + depends on SND_TIMER >> + help >> + Say Y to enable the support of userspace-controlled timers. These >> + timers are purely virtual, and they are supposed to be triggered >> + from userspace. They could be quite useful when synchronizing the >> + sound timing with userspace applications (for instance, when >> sending >> + data through snd-aloop). >> + > > Unneeded extra new line. > >> + >> config SND_VMASTER >> bool > > ... > >> +static void snd_utimer_free(struct snd_utimer *utimer) >> +{ >> + snd_timer_free(utimer->timer); >> + snd_utimer_put_id(utimer); > > Missing kfree(utimer->name); ? > Yeah, it definitely should be here... Thank you for finding this! >> + kfree(utimer); >> +} > > ... > >> +static int snd_utimer_create(struct snd_utimer_info *utimer_info, >> + struct snd_utimer **r_utimer) >> +{ >> + struct snd_utimer *utimer; >> + struct snd_timer *timer; >> + struct snd_timer_id tid; >> + int utimer_id; >> + int err = 0; >> + char *timer_name; >> + >> + utimer = kzalloc(sizeof(*utimer), GFP_KERNEL); >> + if (!utimer) >> + return -ENOMEM; >> + >> + timer_name = kzalloc(SNDRV_UTIMER_NAME_LEN, GFP_KERNEL); > > kasprintf(GFP_KERNEL, "snd-utimer%d", utimer_id); ? > and SNDRV_UTIMER_NAME_LEN becomes useless too. > > In snd_timer_new() it is copied in a char[64] anyway, and if utimer_id > is small, we could even save a few bytes of memory. > Wow, cool, I haven't heard of kasprintf but now I'll use it here in V2. Thanks!
On 7/28/24 07:59, Christophe JAILLET wrote: > Le 26/07/2024 à 09:47, Ivan Orlov a écrit : >> Implement two ioctl calls in order to support virtual userspace-driven >> ALSA timers. >> >> The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the >> snd_utimer_info struct as a parameter and returns a file descriptor of >> a virtual timer. It also updates the `id` field of the snd_utimer_info >> struct, which provides a unique identifier for the timer (basically, >> the subdevice number which can be used when creating timer instances). >> >> This patch also introduces a tiny id allocator for the userspace-driven >> timers, which guarantees that we don't have more than 128 of them in the >> system. >> >> Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger >> the virtual timer (and calls snd_timer_interrupt for the timer under >> the hood), causing all of the timer instances binded to this timer to >> execute their callbacks. >> >> The maximum amount of ticks available for the timer is 1 for the sake of >> simplification of the userspace API. 'start', 'stop', 'open' and 'close' >> callbacks for the userspace-driven timers are empty since we don't >> really do any hardware initialization here. >> >> Suggested-by: Axel Holzinger <aholzinger@gmx.de> >> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> >> --- > > ... > >> +#ifdef CONFIG_SND_UTIMER >> +/* >> + * Since userspace-driven timers are passed to userspace, we need to >> have an identifier >> + * which will allow us to use them (basically, the subdevice number >> of udriven timer). >> + * >> + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to >> (SNDRV_UTIMERS_MAX_COUNT - 1). >> + * When we take one of them, the corresponding entry in >> snd_utimer_ids becomes true. >> + */ >> +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; >> + >> +static void snd_utimer_put_id(struct snd_utimer *utimer) >> +{ >> + int timer_id = utimer->id; >> + >> + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); >> + snd_utimer_ids[timer_id] = false; >> +} >> + >> +static int snd_utimer_take_id(void) >> +{ >> + size_t i; >> + >> + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { >> + if (!snd_utimer_ids[i]) { >> + snd_utimer_ids[i] = true; >> + return i; >> + } >> + } >> + >> + return -EBUSY; >> +} > > Also the bitmap API could be useful here. > Awesome, will use it in V2. Thank you!
Le 28/07/2024 à 10:51, Ivan Orlov a écrit : > On 7/28/24 07:59, Christophe JAILLET wrote: >> Le 26/07/2024 à 09:47, Ivan Orlov a écrit : >>> Implement two ioctl calls in order to support virtual userspace-driven >>> ALSA timers. >>> >>> The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the >>> snd_utimer_info struct as a parameter and returns a file descriptor of >>> a virtual timer. It also updates the `id` field of the snd_utimer_info >>> struct, which provides a unique identifier for the timer (basically, >>> the subdevice number which can be used when creating timer instances). >>> >>> This patch also introduces a tiny id allocator for the userspace-driven >>> timers, which guarantees that we don't have more than 128 of them in the >>> system. >>> >>> Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger >>> the virtual timer (and calls snd_timer_interrupt for the timer under >>> the hood), causing all of the timer instances binded to this timer to >>> execute their callbacks. >>> >>> The maximum amount of ticks available for the timer is 1 for the sake of >>> simplification of the userspace API. 'start', 'stop', 'open' and 'close' >>> callbacks for the userspace-driven timers are empty since we don't >>> really do any hardware initialization here. >>> >>> Suggested-by: Axel Holzinger <aholzinger@gmx.de> >>> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> >>> --- >> >> ... >> >>> +#ifdef CONFIG_SND_UTIMER >>> +/* >>> + * Since userspace-driven timers are passed to userspace, we need to >>> have an identifier >>> + * which will allow us to use them (basically, the subdevice number >>> of udriven timer). >>> + * >>> + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to >>> (SNDRV_UTIMERS_MAX_COUNT - 1). >>> + * When we take one of them, the corresponding entry in >>> snd_utimer_ids becomes true. >>> + */ >>> +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; >>> + >>> +static void snd_utimer_put_id(struct snd_utimer *utimer) >>> +{ >>> + int timer_id = utimer->id; >>> + >>> + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); >>> + snd_utimer_ids[timer_id] = false; >>> +} >>> + >>> +static int snd_utimer_take_id(void) >>> +{ >>> + size_t i; >>> + >>> + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { >>> + if (!snd_utimer_ids[i]) { >>> + snd_utimer_ids[i] = true; >>> + return i; >>> + } >>> + } >>> + >>> + return -EBUSY; >>> +} >> >> Also the bitmap API could be useful here. >> > > Awesome, will use it in V2. Hmm, maybe DEFINE_IDA(), ida_alloc_max() and ida_free() would be even better. CJ > > Thank you! > >
On 7/28/24 10:30, Christophe JAILLET wrote: > Le 28/07/2024 à 10:51, Ivan Orlov a écrit : >> On 7/28/24 07:59, Christophe JAILLET wrote: >>> Le 26/07/2024 à 09:47, Ivan Orlov a écrit : >>>> Implement two ioctl calls in order to support virtual userspace-driven >>>> ALSA timers. >>>> >>>> The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the >>>> snd_utimer_info struct as a parameter and returns a file descriptor of >>>> a virtual timer. It also updates the `id` field of the snd_utimer_info >>>> struct, which provides a unique identifier for the timer (basically, >>>> the subdevice number which can be used when creating timer instances). >>>> >>>> This patch also introduces a tiny id allocator for the userspace-driven >>>> timers, which guarantees that we don't have more than 128 of them in >>>> the >>>> system. >>>> >>>> Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger >>>> the virtual timer (and calls snd_timer_interrupt for the timer under >>>> the hood), causing all of the timer instances binded to this timer to >>>> execute their callbacks. >>>> >>>> The maximum amount of ticks available for the timer is 1 for the >>>> sake of >>>> simplification of the userspace API. 'start', 'stop', 'open' and >>>> 'close' >>>> callbacks for the userspace-driven timers are empty since we don't >>>> really do any hardware initialization here. >>>> >>>> Suggested-by: Axel Holzinger <aholzinger@gmx.de> >>>> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> >>>> --- >>> >>> ... >>> >>>> +#ifdef CONFIG_SND_UTIMER >>>> +/* >>>> + * Since userspace-driven timers are passed to userspace, we need >>>> to have an identifier >>>> + * which will allow us to use them (basically, the subdevice number >>>> of udriven timer). >>>> + * >>>> + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to >>>> (SNDRV_UTIMERS_MAX_COUNT - 1). >>>> + * When we take one of them, the corresponding entry in >>>> snd_utimer_ids becomes true. >>>> + */ >>>> +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; >>>> + >>>> +static void snd_utimer_put_id(struct snd_utimer *utimer) >>>> +{ >>>> + int timer_id = utimer->id; >>>> + >>>> + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); >>>> + snd_utimer_ids[timer_id] = false; >>>> +} >>>> + >>>> +static int snd_utimer_take_id(void) >>>> +{ >>>> + size_t i; >>>> + >>>> + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { >>>> + if (!snd_utimer_ids[i]) { >>>> + snd_utimer_ids[i] = true; >>>> + return i; >>>> + } >>>> + } >>>> + >>>> + return -EBUSY; >>>> +} >>> >>> Also the bitmap API could be useful here. >>> >> >> Awesome, will use it in V2. > > Hmm, maybe DEFINE_IDA(), ida_alloc_max() and ida_free() would be even > better. > It looks like IDA allocator uses XArrays under the hood to allocate ids between 0 and INT_MAX... Considering the fact, that we currently could have up to 128 userspace-driven timers in the system, using XArrays seems a bit redundant, and I believe bitmap approach would be more efficient. What do you think?
Le 28/07/2024 à 11:42, Ivan Orlov a écrit : > On 7/28/24 10:30, Christophe JAILLET wrote: >> Le 28/07/2024 à 10:51, Ivan Orlov a écrit : >>> On 7/28/24 07:59, Christophe JAILLET wrote: >>>> Le 26/07/2024 à 09:47, Ivan Orlov a écrit : >>>>> Implement two ioctl calls in order to support virtual userspace-driven >>>>> ALSA timers. >>>>> >>>>> The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the >>>>> snd_utimer_info struct as a parameter and returns a file descriptor of >>>>> a virtual timer. It also updates the `id` field of the snd_utimer_info >>>>> struct, which provides a unique identifier for the timer (basically, >>>>> the subdevice number which can be used when creating timer instances). >>>>> >>>>> This patch also introduces a tiny id allocator for the >>>>> userspace-driven >>>>> timers, which guarantees that we don't have more than 128 of them >>>>> in the >>>>> system. >>>>> >>>>> Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger >>>>> the virtual timer (and calls snd_timer_interrupt for the timer under >>>>> the hood), causing all of the timer instances binded to this timer to >>>>> execute their callbacks. >>>>> >>>>> The maximum amount of ticks available for the timer is 1 for the >>>>> sake of >>>>> simplification of the userspace API. 'start', 'stop', 'open' and >>>>> 'close' >>>>> callbacks for the userspace-driven timers are empty since we don't >>>>> really do any hardware initialization here. >>>>> >>>>> Suggested-by: Axel Holzinger <aholzinger@gmx.de> >>>>> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> >>>>> --- >>>> >>>> ... >>>> >>>>> +#ifdef CONFIG_SND_UTIMER >>>>> +/* >>>>> + * Since userspace-driven timers are passed to userspace, we need >>>>> to have an identifier >>>>> + * which will allow us to use them (basically, the subdevice >>>>> number of udriven timer). >>>>> + * >>>>> + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to >>>>> (SNDRV_UTIMERS_MAX_COUNT - 1). >>>>> + * When we take one of them, the corresponding entry in >>>>> snd_utimer_ids becomes true. >>>>> + */ >>>>> +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; >>>>> + >>>>> +static void snd_utimer_put_id(struct snd_utimer *utimer) >>>>> +{ >>>>> + int timer_id = utimer->id; >>>>> + >>>>> + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); >>>>> + snd_utimer_ids[timer_id] = false; >>>>> +} >>>>> + >>>>> +static int snd_utimer_take_id(void) >>>>> +{ >>>>> + size_t i; >>>>> + >>>>> + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { >>>>> + if (!snd_utimer_ids[i]) { >>>>> + snd_utimer_ids[i] = true; >>>>> + return i; >>>>> + } >>>>> + } >>>>> + >>>>> + return -EBUSY; >>>>> +} >>>> >>>> Also the bitmap API could be useful here. >>>> >>> >>> Awesome, will use it in V2. >> >> Hmm, maybe DEFINE_IDA(), ida_alloc_max() and ida_free() would be even >> better. >> > > It looks like IDA allocator uses XArrays under the hood to allocate ids > between 0 and INT_MAX... Considering the fact, that we currently could > have up to 128 userspace-driven timers in the system, using XArrays > seems a bit redundant, and I believe bitmap approach would be more > efficient. What do you think? > I may be wrong but I think that ida allocates hunks for 1024 bits (128 bytes * 8) at a time. (see [1]) So with this extra sape and the sapce for the xarray, it would waste a few bytes of memory, yes. With ida, there is also some locking that may be unnecessary (but harmless) Hoping, I got it right, here are a few numbers: On a x86_64, with allmodconfig: Your initial patch: text data bss dec hex filename 55020 1783 268 57071 deef sound/core/timer.o With ida: 54763 1631 116 56510 dcbe sound/core/timer.o + 128 bytes of runtime memory allocation With bitmap: 54805 1535 132 56472 dc98 sound/core/timer.o I think that the code would be slightly more elegant with ida, but implementing it with a bitmap does not add that much complexity. CJ [1]: https://elixir.bootlin.com/linux/v6.10.2/source/include/linux/idr.h#L238
On 7/28/24 11:29, Christophe JAILLET wrote: > > I may be wrong but I think that ida allocates hunks for 1024 bits (128 > bytes * 8) at a time. (see [1]) > > So with this extra sape and the sapce for the xarray, it would waste a > few bytes of memory, yes. > > With ida, there is also some locking that may be unnecessary (but harmless) > > > Hoping, I got it right, here are a few numbers: > > On a x86_64, with allmodconfig: > > Your initial patch: > text data bss dec hex filename > 55020 1783 268 57071 deef sound/core/timer.o > > With ida: > 54763 1631 116 56510 dcbe sound/core/timer.o > + 128 bytes of runtime memory allocation > > With bitmap: > 54805 1535 132 56472 dc98 sound/core/timer.o > > > I think that the code would be slightly more elegant with ida, but > implementing it with a bitmap does not add that much complexity. > Ah, alright, I agree that the code would be cleaner when using IDA, and such a small memory overhead won't be significant/noticeable. I'm going to use IDA in the V2 instead of bitmap API, thank you so much for pointing me to it (I was wondering if the Kernel has a generic ID allocator and now I finally know it does :) ). Thank you!
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h index 8bf7e8a0eb6f..ade952a54edd 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -894,6 +894,7 @@ enum { #define SNDRV_TIMER_GLOBAL_RTC 1 /* unused */ #define SNDRV_TIMER_GLOBAL_HPET 2 #define SNDRV_TIMER_GLOBAL_HRTIMER 3 +#define SNDRV_TIMER_GLOBAL_UDRIVEN 4 /* info flags */ #define SNDRV_TIMER_FLG_SLAVE (1<<0) /* cannot be controlled */ @@ -974,6 +975,20 @@ struct snd_timer_status { }; #endif +/* + * This structure describes the userspace-driven timer. Such timers are purely virtual, + * and can only be triggered from software (for instance, by userspace application). + */ +struct snd_utimer_info { + /* + * To pretend being a normal timer, we need to know the frame rate and + * the period size in frames. + */ + snd_pcm_uframes_t frame_rate; + snd_pcm_uframes_t period_size; + unsigned int id; +}; + #define SNDRV_TIMER_IOCTL_PVERSION _IOR('T', 0x00, int) #define SNDRV_TIMER_IOCTL_NEXT_DEVICE _IOWR('T', 0x01, struct snd_timer_id) #define SNDRV_TIMER_IOCTL_TREAD_OLD _IOW('T', 0x02, int) @@ -990,6 +1005,8 @@ struct snd_timer_status { #define SNDRV_TIMER_IOCTL_CONTINUE _IO('T', 0xa2) #define SNDRV_TIMER_IOCTL_PAUSE _IO('T', 0xa3) #define SNDRV_TIMER_IOCTL_TREAD64 _IOW('T', 0xa4, int) +#define SNDRV_TIMER_IOCTL_CREATE _IOWR('T', 0xa5, struct snd_utimer_info) +#define SNDRV_TIMER_IOCTL_TRIGGER _IO('T', 0xa6) #if __BITS_PER_LONG == 64 #define SNDRV_TIMER_IOCTL_TREAD SNDRV_TIMER_IOCTL_TREAD_OLD diff --git a/sound/core/Kconfig b/sound/core/Kconfig index b970a1734647..3cf82641fc67 100644 --- a/sound/core/Kconfig +++ b/sound/core/Kconfig @@ -251,6 +251,17 @@ config SND_JACK_INJECTION_DEBUG Say Y if you are debugging via jack injection interface. If unsure select "N". +config SND_UTIMER + bool "Enable support for userspace-controlled virtual timers" + depends on SND_TIMER + help + Say Y to enable the support of userspace-controlled timers. These + timers are purely virtual, and they are supposed to be triggered + from userspace. They could be quite useful when synchronizing the + sound timing with userspace applications (for instance, when sending + data through snd-aloop). + + config SND_VMASTER bool diff --git a/sound/core/timer.c b/sound/core/timer.c index d104adc75a8b..177bd06f7b60 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -13,6 +13,8 @@ #include <linux/module.h> #include <linux/string.h> #include <linux/sched/signal.h> +#include <linux/anon_inodes.h> +#include <linux/units.h> #include <sound/core.h> #include <sound/timer.h> #include <sound/control.h> @@ -109,6 +111,17 @@ struct snd_timer_status64 { unsigned char reserved[64]; /* reserved */ }; +#ifdef CONFIG_SND_UTIMER +#define SNDRV_UTIMERS_MAX_COUNT 128 +#define SNDRV_UTIMER_NAME_LEN 20 +/* Internal data structure for keeping the state of the userspace-driven timer */ +struct snd_utimer { + char *name; + struct snd_timer *timer; + unsigned int id; +}; +#endif + #define SNDRV_TIMER_IOCTL_STATUS64 _IOR('T', 0x14, struct snd_timer_status64) /* list of timers */ @@ -2009,6 +2022,217 @@ enum { SNDRV_TIMER_IOCTL_PAUSE_OLD = _IO('T', 0x23), }; +#ifdef CONFIG_SND_UTIMER +/* + * Since userspace-driven timers are passed to userspace, we need to have an identifier + * which will allow us to use them (basically, the subdevice number of udriven timer). + * + * We have a pool of SNDRV_UTIMERS_MAX_COUNT ids from 0 to (SNDRV_UTIMERS_MAX_COUNT - 1). + * When we take one of them, the corresponding entry in snd_utimer_ids becomes true. + */ +static bool snd_utimer_ids[SNDRV_UTIMERS_MAX_COUNT]; + +static void snd_utimer_put_id(struct snd_utimer *utimer) +{ + int timer_id = utimer->id; + + snd_BUG_ON(timer_id < 0 || timer_id >= SNDRV_UTIMERS_MAX_COUNT); + snd_utimer_ids[timer_id] = false; +} + +static int snd_utimer_take_id(void) +{ + size_t i; + + for (i = 0; i < SNDRV_UTIMERS_MAX_COUNT; i++) { + if (!snd_utimer_ids[i]) { + snd_utimer_ids[i] = true; + return i; + } + } + + return -EBUSY; +} + +static void snd_utimer_free(struct snd_utimer *utimer) +{ + snd_timer_free(utimer->timer); + snd_utimer_put_id(utimer); + kfree(utimer); +} + +static int snd_utimer_release(struct inode *inode, struct file *file) +{ + struct snd_utimer *utimer = (struct snd_utimer *)file->private_data; + + snd_utimer_free(utimer); + return 0; +} + +static int snd_utimer_trigger(struct file *file) +{ + struct snd_utimer *utimer = (struct snd_utimer *)file->private_data; + + snd_timer_interrupt(utimer->timer, utimer->timer->sticks); + return 0; +} + +static long snd_utimer_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) +{ + switch (ioctl) { + case SNDRV_TIMER_IOCTL_TRIGGER: + return snd_utimer_trigger(file); + } + + return -ENOTTY; +} + +static const struct file_operations snd_utimer_fops = { + .llseek = noop_llseek, + .release = snd_utimer_release, + .unlocked_ioctl = snd_utimer_ioctl, +}; + +static int snd_utimer_start(struct snd_timer *t) +{ + return 0; +} + +static int snd_utimer_stop(struct snd_timer *t) +{ + return 0; +} + +static int snd_utimer_open(struct snd_timer *t) +{ + return 0; +} + +static int snd_utimer_close(struct snd_timer *t) +{ + return 0; +} + +static const struct snd_timer_hardware timer_hw = { + .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_WORK, + .open = snd_utimer_open, + .close = snd_utimer_close, + .start = snd_utimer_start, + .stop = snd_utimer_stop, +}; + +static int snd_utimer_create(struct snd_utimer_info *utimer_info, + struct snd_utimer **r_utimer) +{ + struct snd_utimer *utimer; + struct snd_timer *timer; + struct snd_timer_id tid; + int utimer_id; + int err = 0; + char *timer_name; + + utimer = kzalloc(sizeof(*utimer), GFP_KERNEL); + if (!utimer) + return -ENOMEM; + + timer_name = kzalloc(SNDRV_UTIMER_NAME_LEN, GFP_KERNEL); + if (!timer_name) { + kfree(utimer); + return -ENOMEM; + } + + /* We hold the ioctl lock here so we won't get a race condition when allocating id */ + utimer_id = snd_utimer_take_id(); + if (utimer_id < 0) { + err = utimer_id; + goto err_take_id; + } + + sprintf(timer_name, "snd-utimer%d", utimer_id); + utimer->name = timer_name; + utimer->id = utimer_id; + + tid.dev_sclass = SNDRV_TIMER_SCLASS_APPLICATION; + tid.dev_class = SNDRV_TIMER_CLASS_GLOBAL; + tid.card = -1; + tid.device = SNDRV_TIMER_GLOBAL_UDRIVEN; + tid.subdevice = utimer_id; + + err = snd_timer_new(NULL, timer_name, &tid, &timer); + if (err < 0) { + pr_err("Can't create userspace-driven timer\n"); + goto err_timer_new; + } + + timer->module = THIS_MODULE; + timer->hw = timer_hw; + timer->hw.resolution = NANO / utimer_info->frame_rate * utimer_info->period_size; + timer->hw.ticks = 1; + timer->max_instances = MAX_SLAVE_INSTANCES; + + utimer->timer = timer; + + err = snd_timer_global_register(timer); + if (err < 0) { + pr_err("Can't register a userspace-driven timer\n"); + goto err_timer_reg; + } + + *r_utimer = utimer; + return 0; + +err_timer_reg: + snd_timer_free(timer); +err_timer_new: + snd_utimer_put_id(utimer); +err_take_id: + kfree(timer_name); + kfree(utimer); + + return err; +} + +static int snd_utimer_ioctl_create(struct file *file, + struct snd_utimer_info __user *_utimer_info) +{ + struct snd_utimer *utimer; + struct snd_utimer_info *utimer_info; + int err; + + utimer_info = memdup_user(_utimer_info, sizeof(*utimer_info)); + if (IS_ERR(utimer_info)) + return PTR_ERR(no_free_ptr(utimer_info)); + + err = snd_utimer_create(utimer_info, &utimer); + if (err < 0) { + kfree(utimer_info); + return err; + } + + utimer_info->id = utimer->id; + + err = copy_to_user(_utimer_info, utimer_info, sizeof(*utimer_info)); + if (err) { + snd_utimer_free(utimer); + kfree(utimer_info); + return -EFAULT; + } + + kfree(utimer_info); + + return anon_inode_getfd(utimer->name, &snd_utimer_fops, utimer, O_RDWR | O_CLOEXEC); +} + +#else + +static int snd_utimer_ioctl_create(struct file *file, + struct snd_utimer_info __user *_utimer_info) +{ + return -EINVAL; +} + +#endif + static long __snd_timer_user_ioctl(struct file *file, unsigned int cmd, unsigned long arg, bool compat) { @@ -2053,6 +2277,8 @@ static long __snd_timer_user_ioctl(struct file *file, unsigned int cmd, case SNDRV_TIMER_IOCTL_PAUSE: case SNDRV_TIMER_IOCTL_PAUSE_OLD: return snd_timer_user_pause(file); + case SNDRV_TIMER_IOCTL_CREATE: + return snd_utimer_ioctl_create(file, argp); } return -ENOTTY; }
Implement two ioctl calls in order to support virtual userspace-driven ALSA timers. The first ioctl is SNDRV_TIMER_IOCTL_CREATE, which gets the snd_utimer_info struct as a parameter and returns a file descriptor of a virtual timer. It also updates the `id` field of the snd_utimer_info struct, which provides a unique identifier for the timer (basically, the subdevice number which can be used when creating timer instances). This patch also introduces a tiny id allocator for the userspace-driven timers, which guarantees that we don't have more than 128 of them in the system. Another ioctl is SNDRV_TIMER_IOCTL_TRIGGER, which allows us to trigger the virtual timer (and calls snd_timer_interrupt for the timer under the hood), causing all of the timer instances binded to this timer to execute their callbacks. The maximum amount of ticks available for the timer is 1 for the sake of simplification of the userspace API. 'start', 'stop', 'open' and 'close' callbacks for the userspace-driven timers are empty since we don't really do any hardware initialization here. Suggested-by: Axel Holzinger <aholzinger@gmx.de> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com> --- include/uapi/sound/asound.h | 17 +++ sound/core/Kconfig | 11 ++ sound/core/timer.c | 226 ++++++++++++++++++++++++++++++++++++ 3 files changed, 254 insertions(+)