30 Aug
2005
30 Aug
'05
5:07 p.m.
Dear wise members of the list.
I am (still) trying to implement a control panel
feature for the U2A USB sound card. I (finally!) have
the alsa patch from Clemens Ladisch up and running -
at least I can compile a small program that when run
squirts of a small control transfer URB to the sound
card without complaints.
Now, half of the URBs sent to the device are
CONTROL_TRANSFER blocks, but the other half are marked
as CLASS_INTERFACE in the SnoopyPro logs. See a
typical example below.
I have googled the net and searched the USB specs
without getting much wiser as to what a
CLASS_INTERFACE request is and does. Can I send it
using CONTROL_TRANSFER URBs or is yet another
extension of the alsa driver necessary ?
Cheers
-- Jan Holst
277 out down n/a 710.461
CLASS_INTERFACE 01
URB Header (length: 80)
SequenceNumber: 277
Function: 001b (CLASS_INTERFACE)
PipeHandle: 00000001
SetupPacket:
0000: 00 01 00 01 00 04 ea 87
bmRequestType: 00
DIR: Host-To-Device
TYPE: Standard
RECIPIENT: Device
bRequest: 01
CLEAR_FEATURE
TransferBuffer: 0x00000001 (1) length
0000: 01
277 out up n/a 710.471 CONTROL_TRANSFER
- 0x00000000
URB Header (length: 80)
SequenceNumber: 277
Function: 0008 (CONTROL_TRANSFER)
PipeHandle: 860fee14
SetupPacket:
0000: 21 01 00 01 00 04 01 00
bmRequestType: 21
DIR: Host-To-Device
TYPE: Class
RECIPIENT: Interface
bRequest: 01
No TransferBuffer
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30 Aug
30 Aug
5:32 p.m.
On Tue, 2005-08-30 at 14:07 -0700, Jan Holst Jensen wrote:
Dear wise members of the list.
I am (still) trying to implement a control panel
feature for the U2A USB sound card. I (finally!) have
the alsa patch from Clemens Ladisch up and running -
at least I can compile a small program that when run
squirts of a small control transfer URB to the sound
card without complaints.
This is a better question for the alsa-devel list. This list is mostly
for userspace stuff.
Lee
31 Aug
31 Aug
9:53 a.m.
I am (still)
trying to implement a control panel
feature for the U2A USB sound card. I (finally!)
have
the alsa patch from Clemens Ladisch up and
running
-
at least I can compile a small program that when
run
squirts of a small control transfer URB to the
sound
card without complaints.
This is a better question for the alsa-devel list.
This list is mostly for userspace stuff. 
4:36 a.m.
Jan Holst Jensen wrote:
I am (still) trying to implement a control panel
feature for the U2A USB sound card.
Now, half of the URBs sent to the device are
CONTROL_TRANSFER blocks, but the other half are marked
as CLASS_INTERFACE in the SnoopyPro logs. See a
typical example below.
SnoopyPro doesn't label all packets correctly. It seems the
bmRequestType field hasn't yet been filled when the 'down' request is
logged, so you have to look at the corresponding 'up' data.
I have googled the net and searched the USB specs
without getting much wiser as to what a
CLASS_INTERFACE request is and does.
"CLASS" means that the meaning of the bRequest field is class-specific
-- in this case, defined in the USB audio specification.
To determine what the other fields mean, get the unit ID from the
upper byte of the wIndex field (sixth byte in the setup packet),
search for the unit in the descriptors, and then look up that unit
type in the USB audio spec.
Can I send it using CONTROL_TRANSFER URBs or is yet
another
extension of the alsa driver necessary ?
With USB audio devices, all transfers (except the audio data itself)
are control transfers.
SetupPacket:
0000: 21 01 00 01 00 04 01 00
bRequestType: 0x21 CLASS_INTERFACE, out
bRequest: 0x01 SET_CUR
wValue: 0x0100 control/channel? #1 (MSB) of this unit
wIndex: 0x0400 interface #0 (LSB), unit #4 (MSB)
wLength: 0x0001
I guess that unit 4 is a Selector Unit, because most other types would
require a two-byte buffer.
HTH
Clemens
9:57 a.m.
"CLASS" means that the meaning of the
bRequest field
is class-specific
-- in this case, defined in the USB audio
specification.
Aha.
To determine what the other fields mean, get the
unit ID from the
upper byte of the wIndex field (sixth byte in the
setup packet),
search for the unit in the descriptors, and then
look up that unit
type in the USB audio spec.
OK - its starting to make sense.
Can I send it
using CONTROL_TRANSFER URBs or is
yet another
extension of the alsa driver necessary ?
With USB audio devices, all transfers (except the
audio data itself)
are control transfers. SetupPacket:
0000: 21 01 00 01 00 04 01 00
bRequestType: 0x21 CLASS_INTERFACE, out
bRequest: 0x01 SET_CUR
wValue: 0x0100 control/channel? #1 (MSB) of
this unit
wIndex: 0x0400 interface #0 (LSB), unit #4
(MSB)
wLength: 0x0001
I guess that unit 4 is a Selector Unit, because most
other types would require a two-byte buffer.
7061
days inactive
7062
days old
linux-audio-dev@lists.linuxaudio.org
4 comments
3 participants
participants (3)
-
Clemens Ladisch -
Jan Holst Jensen -
Lee Revell