[alsa-devel] [PATCH] ALSA: usb-audio: Recurse before saving terminal properties
When the descriptor parser recurses into the clock source descriptor, the terminals properties, like name and type, are set to the values of the clock selector as check_input_term overwrites term->name and others in the recursive call. As we want to only fill missing values using the descriptors higher in the recursion tree the properties taken from the actual descriptor must be applied after recursing.
Signed-off-by: Julian Scheel julian@jusst.de --- sound/usb/mixer.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 6b3acba..4a49944 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1; - term->type = le16_to_cpu(d->wTerminalType); - term->channels = d->bNrChannels; - term->chconfig = le32_to_cpu(d->bmChannelConfig); - term->name = d->iTerminal;
/* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err; + + term->type = le16_to_cpu(d->wTerminalType); + term->channels = d->bNrChannels; + term->chconfig = le32_to_cpu(d->bmChannelConfig); + term->name = d->iTerminal; } return 0; case UAC_FEATURE_UNIT: {
On Wed, 12 Aug 2015 22:14:59 +0200, Julian Scheel wrote:
When the descriptor parser recurses into the clock source descriptor, the terminals properties, like name and type, are set to the values of the clock selector as check_input_term overwrites term->name and others in the recursive call. As we want to only fill missing values using the descriptors higher in the recursion tree the properties taken from the actual descriptor must be applied after recursing.
Signed-off-by: Julian Scheel julian@jusst.de
Thanks for the patch. I vaguely remember of a similar patch, maybe you who already sent. One thing I find uncertain is whether this breaks the current logic completely, namely:
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;
... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
Maybe Daniel can answer better how the original code is supposed to work. Daniel?
Takashi
Am 14.08.2015 um 15:06 schrieb Takashi Iwai:
On Wed, 12 Aug 2015 22:14:59 +0200, Julian Scheel wrote:
When the descriptor parser recurses into the clock source descriptor, the terminals properties, like name and type, are set to the values of the clock selector as check_input_term overwrites term->name and others in the recursive call. As we want to only fill missing values using the descriptors higher in the recursion tree the properties taken from the actual descriptor must be applied after recursing.
Signed-off-by: Julian Scheel julian@jusst.de
Thanks for the patch. I vaguely remember of a similar patch, maybe you who already sent.
Hm, I couldn't remember to have sent a similar patch before :)
One thing I find uncertain is whether this breaks the current logic completely, namely:
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
This is a good point indeed, but due do my understanding the recursion is not about filling missing information, but about verifying a valid descriptor. So in case there are broken references in the descriptor it gets abandoned. I'm happy to be corrected if this understanding is wrong.
When overriding the value in the recursion as it is without this patch it leads to virtually any control getting the name of the Clock Selector... I wondered about this on several UAC2 devices (like the XMOS stuff), before I looked into it.
-Julian
Hi,
On 08/14/2015 03:25 PM, Julian Scheel wrote:
Am 14.08.2015 um 15:06 schrieb Takashi Iwai:
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
This is a good point indeed, but due do my understanding the recursion is not about filling missing information, but about verifying a valid descriptor. So in case there are broken references in the descriptor it gets abandoned. I'm happy to be corrected if this understanding is wrong.
Hmm, good point. It' been a while since I worked on this, but looking at the code right now, you're right, the mixer unit for input terminal is indeed just overridden by the information of the clock selector on UAC2. That doesn't seem right.
I guess what we really want is to add a 2nd mixer control in such cases, and that would mean we need to call into parse_audio_selector_unit() instead.
I can cook up or test a patch next week, when I have access to test hardware.
Thanks, Daniel
Hi Daniel,
On 16.08.15 13:45, Daniel Mack wrote:
On 08/14/2015 03:25 PM, Julian Scheel wrote:
Am 14.08.2015 um 15:06 schrieb Takashi Iwai:
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
This is a good point indeed, but due do my understanding the recursion is not about filling missing information, but about verifying a valid descriptor. So in case there are broken references in the descriptor it gets abandoned. I'm happy to be corrected if this understanding is wrong.
Hmm, good point. It' been a while since I worked on this, but looking at the code right now, you're right, the mixer unit for input terminal is indeed just overridden by the information of the clock selector on UAC2. That doesn't seem right.
I guess what we really want is to add a 2nd mixer control in such cases, and that would mean we need to call into parse_audio_selector_unit() instead.
Ah, you're right. The Clock Selector shall actually be exposed as a mixer unit. This never happened with the current code, but it just renamed all other selectors to the name of the clock selector if it existed.
I can cook up or test a patch next week, when I have access to test hardware.
I can update my patch to reflect this as well. If you haven't done before I'll try to do it later today.
-Julian
Hi Daniel,
On 16.08.2015 13:45, Daniel Mack wrote:
Hi,
On 08/14/2015 03:25 PM, Julian Scheel wrote:
Am 14.08.2015 um 15:06 schrieb Takashi Iwai:
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
This is a good point indeed, but due do my understanding the recursion is not about filling missing information, but about verifying a valid descriptor. So in case there are broken references in the descriptor it gets abandoned. I'm happy to be corrected if this understanding is wrong.
Hmm, good point. It' been a while since I worked on this, but looking at the code right now, you're right, the mixer unit for input terminal is indeed just overridden by the information of the clock selector on UAC2. That doesn't seem right.
I guess what we really want is to add a 2nd mixer control in such cases, and that would mean we need to call into parse_audio_selector_unit() instead.
I just had another look at this. In fact all mixer controls are properly created with the current code. This happens in the loop over all descriptors in snd_usb_mixer_controls. parse_audio_unit is called for each of them. For clock selectors and selector units it calls parse_audio_selector_unit where the actual clock selector/selector units are parsed and mixer ctls are created. So I'd renew my first comment about the recursion. It is only needed to verify the integrity of descriptors and hence shall not overwrite any values.
After patching my device to offer 2 clocks on the clock selector the mixer looks like this with my patch: -- Simple mixer control 'Master',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback 0 - 44 Mono: Playback 26 [59%] [-36.00dB] [on] Simple mixer control 'Clock Selector',0 Capabilities: enum Items: 'Internal Clock' 'Fake Clock' Item0: 'Internal Clock' Simple mixer control 'Input Selector',0 Capabilities: enum Items: 'USB' 'S/PDIF' Item0: 'USB' --
Running the same without my patch results in: -- Simple mixer control 'Master',0 Capabilities: pvolume pvolume-joined pswitch pswitch-joined Playback channels: Mono Limits: Playback 0 - 44 Mono: Playback 26 [59%] [-36.00dB] [on] Simple mixer control 'Clock Selector',0 Capabilities: enum Items: 'Internal Clock' 'Fake Clock' Item0: 'Internal Clock' Simple mixer control 'Input Selector',0 Capabilities: enum Items: 'Clock Selector' 'Clock Selector' Item0: 'Clock Selector' --
So you can see, in both cases the mixer controls are generated as it should be. But the original code applies the wrong labels to all the Input Terminals associated to Input Selector. I think keeping the recursion, but not using any of the term values from the recursion is the correct approach as it ensures there are no dead ends in the descriptor hierarchy (i.e. referencing non-existant clock entities), but keeps the actual terminal properties correct. What shall be changed in my original patch is that the term->id shall also be reset after recursing into check_input_term, as otherwise the input terminals are stored with the clock selectors id. Would you agree on that?
Thanks, Julian
On 08/17/2015 10:35 AM, Julian Scheel wrote:
On 16.08.2015 13:45, Daniel Mack wrote:
Hmm, good point. It' been a while since I worked on this, but looking at the code right now, you're right, the mixer unit for input terminal is indeed just overridden by the information of the clock selector on UAC2. That doesn't seem right.
I guess what we really want is to add a 2nd mixer control in such cases, and that would mean we need to call into parse_audio_selector_unit() instead.
I just had another look at this. In fact all mixer controls are properly created with the current code. This happens in the loop over all descriptors in snd_usb_mixer_controls. parse_audio_unit is called for each of them. For clock selectors and selector units it calls parse_audio_selector_unit where the actual clock selector/selector units are parsed and mixer ctls are created. So I'd renew my first comment about the recursion. It is only needed to verify the integrity of descriptors and hence shall not overwrite any values.
Yes, you're right. So your first patch on this is actually correct, but given it caused confusion, I guess it deserves a comment in both the code and the commit log :)
Care to resend with those comments added?
Thanks, Daniel
On 14 August 2015 at 15:06, Takashi Iwai tiwai@suse.de wrote:
On Wed, 12 Aug 2015 22:14:59 +0200, Julian Scheel wrote:
When the descriptor parser recurses into the clock source descriptor, the terminals properties, like name and type, are set to the values of the clock selector as check_input_term overwrites term->name and others in the recursive call. As we want to only fill missing values using the descriptors higher in the recursion tree the properties taken from the actual descriptor must be applied after recursing.
Signed-off-by: Julian Scheel julian@jusst.de
Thanks for the patch. I vaguely remember of a similar patch, maybe you who already sent. One thing I find uncertain is whether this breaks the current logic completely, namely:
Maybe that vague memory relates to me asking about this code a while ago. I never sent any patch though because I couldn't figure out what the correct behaviour should be. Hats off to Julian for fixing it, this is a step on the way to get the Asus U7 fully working.
@@ -715,15 +715,16 @@ static int check_input_term(struct mixer_build *state, int id, term->name = d->iTerminal; } else { /* UAC_VERSION_2 */ struct uac2_input_terminal_descriptor *d = p1;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal; /* call recursively to get the clock selectors */ err = check_input_term(state, d->bCSourceID, term); if (err < 0) return err;
term->type = le16_to_cpu(d->wTerminalType);term->channels = d->bNrChannels;term->chconfig = le32_to_cpu(d->bmChannelConfig);term->name = d->iTerminal;... by this override, essentially all fields except for id are restored. Then what's the point to call check_input_term() for the clock source?
Maybe Daniel can answer better how the original code is supposed to work. Daniel?
Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
participants (4)
-
Daniel Mack -
Johan Aires Rastén -
Julian Scheel -
Takashi Iwai