Questions on usb audio development

Questions on usb audio development

[LCID Fire]

Hi.
I know there is quite some documentation how to develop a pci driver for
alsa - but since I'll try to get a usb device working I was wondering
how to write a usb driver? Is it just the same? How to interface the
various aspects of the device with regards to descriptor reading, ...

Re: Questions on usb audio development

[Lee Revell]

On 5/20/07, LCID Fire <lcid-fire@gmx.net> wrote:
> Hi.
> I know there is quite some documentation how to develop a pci driver for
> alsa - but since I'll try to get a usb device working I was wondering
> how to write a usb driver? Is it just the same? How to interface the
> various aspects of the device with regards to descriptor reading, ...

Look at the snd-usb-audio and usx2y sources.

Lee

Re: Questions on usb audio development

[Takashi Iwai]

At Sun, 20 May 2007 15:25:31 -0400,
Lee Revell wrote:
> 
> On 5/20/07, LCID Fire <lcid-fire@gmx.net> wrote:
> > Hi.
> > I know there is quite some documentation how to develop a pci driver for
> > alsa - but since I'll try to get a usb device working I was wondering
> > how to write a usb driver? Is it just the same? How to interface the
> > various aspects of the device with regards to descriptor reading, ...
> 
> Look at the snd-usb-audio and usx2y sources.

Also the new caiaq driver.

The major difference between the normal PCI and USB audio drivers is
that USB audio has no traditional DMA like most PCI devices have.
Thus the driver has to sets up URB pakets.  usb-audio driver creates
an intermediate ring-buffer that is used for the communication from/to
user-space, and URBs are made from this buffer.


Takashi

Re: Questions on usb audio development

[LCID Fire]

Takashi Iwai wrote:
> The major difference between the normal PCI and USB audio drivers is
> that USB audio has no traditional DMA like most PCI devices have.
> Thus the driver has to sets up URB pakets.  usb-audio driver creates
> an intermediate ring-buffer that is used for the communication from/to
> user-space, and URBs are made from this buffer.

Basicly the reoccuring interface pattern I'm facing is:

bLength                 9
bDescriptorType         4
bInterfaceNumber        5
bAlternateSetting       1
bNumEndpoints           1
bInterfaceClass       255 Vendor Specific Class
bInterfaceSubClass      2
bInterfaceProtocol      0
iInterface              6 LineIn2
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported
	Endpoint Descriptor:
		bLength                 9
		bDescriptorType         5
		bEndpointAddress     0x84  EP 4 IN
		bmAttributes            9
			Transfer Type            Isochronous
			Synch Type               Adaptive
			Usage Type               Data
		wMaxPacketSize     0x00b8  1x 184 bytes
		bInterval               1
		bRefresh                0
		bSynchAddress           0


Which is - if you ask me a normal audio token - hidden as a vendor
specific interface. So what do you think, are these 2 descriptors just
the audio format info or have they really embedded some specific info
for the class? Question is whether to wire that with FIXED_ENDPOINT or
STANDARD_INTERFACE?

The others are:
bLength                 9
bDescriptorType         4
bInterfaceNumber        0
bAlternateSetting       0
bNumEndpoints           0
bInterfaceClass       255 Vendor Specific Class
bInterfaceSubClass      1
bInterfaceProtocol      0
iInterface             15 Line 1
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported
Class specific interface descriptor for class 255 is unsupported

Which again does not seem to be more than the sync node of an audio
device (especially as it seems like they did not even change the subclass).

Well and I just for a start tried to write a quirks sections for these
nodes like:

{
	USB_DEVICE(0x13e5, 0x0001),
	.driver_info = (unsigned long) & (const struct snd_usb_audio_quirk)
	{
		.ifnum = QUIRK_ANY_INTERFACE,
		.type = QUIRK_COMPOSITE,		
		.data = & (const struct snd_usb_audio_quirk[])
		{
			{
				.ifnum = 0,
				.altsetting = 0,
				.type = QUIRK_AUDIO_STANDARD_INTERFACE
			},
			{
				.ifnum = 0,
				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
				.data = & (const struct audioformat)
				{
					.format = SNDRV_PCM_FORMAT_S16_LE,
					.channels = 2,
					.iface = 0,
					.altsetting = 1,
					.altset_idx = 1,
					.attributes = 0,
					.endpoint = 0x01,
					.ep_attr = 0x09,
					.rates = SNDRV_PCM_RATE_CONTINUOUS,
					.rate_min = 44100,
					.rate_max = 44100,
				}
			},
			{
				.ifnum = 2,
				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
				.data = & (const struct audioformat)
				{
					.format = SNDRV_PCM_FORMAT_S16_LE,
					.channels = 2,
					.iface = 2,
					.altsetting = 1,
					.altset_idx = 1,
					.attributes = 0,
					.endpoint = 0x82,
					.ep_attr = 0x09,
					.rates = SNDRV_PCM_RATE_CONTINUOUS,
					.rate_min = 44100,
					.rate_max = 44100,
				}
				
			},
			{
				.ifnum = 3,
				.altsetting = 0,
				.type = QUIRK_AUDIO_STANDARD_INTERFACE
			},
			{
				.ifnum = 4,
				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
				.data = & (const struct audioformat)
				{
					.format = SNDRV_PCM_FORMAT_S16_LE,
					.channels = 2,
					.iface = 4,
					.altsetting = 1,
					.altset_idx = 1,
					.attributes = 0,
					.endpoint = 0x04,
					.ep_attr = 0x09,
					.rates = SNDRV_PCM_RATE_CONTINUOUS,
					.rate_min = 44100,
					.rate_max = 44100,
				}
			},
			{
				.ifnum = 5,
				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
				.data = & (const struct audioformat)
				{
					.format = SNDRV_PCM_FORMAT_S16_LE,
					.channels = 2,
					.iface = 5,
					.altsetting = 1,
					.altset_idx = 1,
					.attributes = 0,
					.endpoint = 0x84,
					.ep_attr = 0x09,
					.rates = SNDRV_PCM_RATE_CONTINUOUS,
					.rate_min = 44100,
					.rate_max = 44100,
				}
			},
			{
				.ifnum = 6,
				.altsetting = 0,
				.type = QUIRK_AUDIO_STANDARD_INTERFACE
			},
			{
				.ifnum = 7,
				.type = QUIRK_AUDIO_FIXED_ENDPOINT,
				.data = & (const struct audioformat)
				{
					.format = SNDRV_PCM_FORMAT_S16_LE,
					.channels = 2,
					.iface = 7,
					.altsetting = 1,
					.altset_idx = 1,
					.attributes = 0,
					.endpoint = 0x85,
					.ep_attr = 0x09,
					.rates = SNDRV_PCM_RATE_CONTINUOUS,
					.rate_min = 44100,
					.rate_max = 44100,
				}
			},
			{
				.ifnum = -1
			}
		}
	}
},

So could anyone please tell me whether I'm totally lost on a wrong track?

Quirks device not showing up

[LCID Fire]

Well I defined a quirks for my usb device. I mined the probe code with
output and it creates a new driver instance for my device as well as it
finds the channels. Nevertheless I don't get my device listed in
userspace. Is there anything special to be done besides defining a quirks?

Re: Quirks device not showing up

[Clemens Ladisch]

LCID Fire wrote:
> Well I defined a quirks for my usb device. I mined the probe code with
> output and it creates a new driver instance for my device as well as it
> finds the channels. Nevertheless I don't get my device listed in
> userspace. Is there anything special to be done besides defining a
> quirks?

All quirks have been written as specific workarounds for certain
devices.  It is possible that you device behaves in some different way.

I'd tell you what the actual problem with your quirk is, but my crystal
ball is under repair just now.  Please show your code and the output of
"lsusb -v" for your device.


Regards,
Clemens

Re: Quirks device not showing up

[LCID Fire]

Clemens Ladisch wrote:
> I'd tell you what the actual problem with your quirk is, but my crystal
> ball is under repair just now.  Please show your code and the output of
> "lsusb -v" for your device.
It's the following:
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.00
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass       255 Vendor Specific Subclass
  bDeviceProtocol       255 Vendor Specific Protocol
  bMaxPacketSize0        32
  idVendor           0x13e5
  idProduct          0x0001
  bcdDevice            1.00
  iManufacturer           1
  iProduct                2
  iSerial                 0
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength          497
    bNumInterfaces          9
    bConfigurationValue     1
    iConfiguration         13
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              300mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1
      bInterfaceProtocol      0
      iInterface             15
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              7
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        1
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              9
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x01  EP 1 OUT
        bmAttributes            9
          Transfer Type            Isochronous
          Synch Type               Adaptive
          Usage Type               Data
        wMaxPacketSize     0x00b8  1x 184 bytes
        bInterval               1
        bRefresh                0
        bSynchAddress           0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              3
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        2
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              5
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x82  EP 2 IN
        bmAttributes            9
          Transfer Type            Isochronous
          Synch Type               Adaptive
          Usage Type               Data
        wMaxPacketSize     0x00b8  1x 184 bytes
        bInterval               1
        bRefresh                0
        bSynchAddress           0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        3
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1
      bInterfaceProtocol      0
      iInterface             16
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        4
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              8
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        4
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface             10
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x04  EP 4 OUT
        bmAttributes            9
          Transfer Type            Isochronous
          Synch Type               Adaptive
          Usage Type               Data
        wMaxPacketSize     0x00b8  1x 184 bytes
        bInterval               1
        bRefresh                0
        bSynchAddress           0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        5
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              4
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        5
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface              6
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x84  EP 4 IN
        bmAttributes            9
          Transfer Type            Isochronous
          Synch Type               Adaptive
          Usage Type               Data
        wMaxPacketSize     0x00b8  1x 184 bytes
        bInterval               1
        bRefresh                0
        bSynchAddress           0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        6
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      1
      bInterfaceProtocol      0
      iInterface             17
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        7
      bAlternateSetting       0
      bNumEndpoints           0
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface             11
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        7
      bAlternateSetting       1
      bNumEndpoints           1
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      2
      bInterfaceProtocol      0
      iInterface             12
      Class specific interface descriptor for class 255 is unsupported
      Class specific interface descriptor for class 255 is unsupported
      Endpoint Descriptor:
        bLength                 9
        bDescriptorType         5
        bEndpointAddress     0x85  EP 5 IN
        bmAttributes            9
          Transfer Type            Isochronous
          Synch Type               Adaptive
          Usage Type               Data
        wMaxPacketSize     0x0090  1x 144 bytes
        bInterval               1
        bRefresh                0
        bSynchAddress           0
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        8
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass      0
      bInterfaceProtocol      0
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x83  EP 3 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               4
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0040  1x 64 bytes
        bInterval               4
cannot read device status, Operation not permitted (1)

Seems pretty default to me. As I said the probing and analyses of the
channel seems to work fine.

Re: Quirks device not showing up

[Lee Revell]

On 6/8/07, LCID Fire <lcid-fire@gmx.net> wrote:
> Clemens Ladisch wrote:
> > I'd tell you what the actual problem with your quirk is, but my crystal
> > ball is under repair just now.  Please show your code and the output of
> > "lsusb -v" for your device.
> It's the following:

Where's the code?

Lee

Re: Quirks device not showing up

[LCID Fire]

Lee Revell wrote:
> On 6/8/07, LCID Fire <lcid-fire@gmx.net> wrote:
>> Clemens Ladisch wrote:
>>> I'd tell you what the actual problem with your quirk is, but my crystal
>>> ball is under repair just now.  Please show your code and the output of
>>> "lsusb -v" for your device.
>> It's the following:
> 
> Where's the code?
Oh, it's

{
	USB_DEVICE(0x13e5, 0x0001),
	.driver_info = (unsigned long) & (const struct snd_usb_audio_quirk)
	{
		.ifnum = QUIRK_ANY_INTERFACE,
		.type = QUIRK_AUDIO_STANDARD_INTERFACE
	}
}

added to usbquirks.h

Re: Quirks device not showing up

[LCID Fire]

LCID Fire wrote:
> Well I defined a quirks for my usb device. I mined the probe code with
> output and it creates a new driver instance for my device as well as it
> finds the channels. Nevertheless I don't get my device listed in
> userspace. Is there anything special to be done besides defining a quirks?
I have to correct myself a bit. The patch is actually working - and my
card and it's channels are detected just fine - problem is there seems
to be no mixer available for my channels.
When I try to access my card using alsamixer I get a message "No mixer
elems found". Is there a special .conf file necessary and what's the
format for it?

Re: Quirks device not showing up

[Lee Revell]

On 6/11/07, LCID Fire <lcid-fire@gmx.net> wrote:
> LCID Fire wrote:
> > Well I defined a quirks for my usb device. I mined the probe code with
> > output and it creates a new driver instance for my device as well as it
> > finds the channels. Nevertheless I don't get my device listed in
> > userspace. Is there anything special to be done besides defining a quirks?
> I have to correct myself a bit. The patch is actually working - and my
> card and it's channels are detected just fine - problem is there seems
> to be no mixer available for my channels.
> When I try to access my card using alsamixer I get a message "No mixer
> elems found". Is there a special .conf file necessary and what's the
> format for it?

This is normal, many USB devices don't have any mixer elements.

Lee

Re: Quirks device not showing up

[LCID Fire]

Lee Revell wrote:
> On 6/11/07, LCID Fire <lcid-fire@gmx.net> wrote:
>> I have to correct myself a bit. The patch is actually working - and my
>> card and it's channels are detected just fine - problem is there seems
>> to be no mixer available for my channels.
>> When I try to access my card using alsamixer I get a message "No mixer
>> elems found". Is there a special .conf file necessary and what's the
>> format for it?
> 
> This is normal, many USB devices don't have any mixer elements.
Ok, but isn't there a software way to emulate the mixer?