On 31. 07. 24 12:30, Takashi Iwai wrote:
On Tue, 30 Jul 2024 16:55:19 +0200,
Jaroslav Kysela wrote:
On 30. 07. 24 16:37, Stefan Binding wrote:
Add a kernel parameter to allow coefficients to be exposed as ALSA controls.
When the CS35L41 loads its firmware, it has a number of controls to
affect its behaviour. Currently, these controls are exposed as ALSA
Controls by default.
However, nothing in userspace currently uses them, and is unlikely to
do so in the future, therefore we don't need to create ASLA controls
for them.
These controls can be useful for debug, so we can add a kernel
parameter to re-enable them if necessary.
Disabling these controls would prevent userspace from trying to read
these controls when the CS35L41 is hibernating, which ordinarily
would result in an error message.
This is probably not a right argument to add this code. The codec
should be powered up when those controls are accessed or those
controls should be cached by the driver.
Although the controls have not been used yet, exposing them in this
way is not ideal.
Could you fix the driver (no I/O errors)?
While we should fix the potential errors at hibernation, it's not bad
to hide those controls, IMO. For the normal use cases, it's nothing
but a cause of troubles, after all.
I do not think that the situation is so obvious. Different coefficients can be
used in various UCM profiles for example.
But for debugging we have debugfs when the developer thinks that the feature
is not useful for users. The module parameter solution is not good in my eyes.
Jaroslav
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
