[alsa-devel] Mixer control for signed gain value
Hi,
The CODEC I am working with takes byte-long gain value in two's complement form. In soc-core.c, the closest functions I see are snd_soc_info_volsw_s8 snd_soc_get_volsw_s8 snd_soc_set_volsw_s8
These functions are coded to work with two integer values. For my purpose, I suppose that I can always set 2nd integer input as zero. However, would I still be able to set volume like amixer sset "Codec Gain" 100 as percentage. If yes, how will amixer know to put upper 8 bits of 16 bit gain in 2nd integer value element?
Thanks Patrick
On Wed, Jun 22, 2011 at 11:32:19PM -0700, Patrick Lai wrote:
The CODEC I am working with takes byte-long gain value in two's complement form. In soc-core.c, the closest functions I see are snd_soc_info_volsw_s8 snd_soc_get_volsw_s8 snd_soc_set_volsw_s8
These functions are coded to work with two integer values. For my purpose, I suppose that I can always set 2nd integer input as zero. However, would I still be able to set volume like amixer sset "Codec Gain" 100 as percentage. If yes, how will amixer know to put upper 8 bits of 16 bit gain in 2nd integer value element?
Could you clarify what the control you're dealing with is? You say above that your gains are byte long but here you're talking about them actually being 16 bit. If they're 16 bit you probably need to write a new control type.
On 6/23/2011 3:37 AM, Mark Brown wrote:
On Wed, Jun 22, 2011 at 11:32:19PM -0700, Patrick Lai wrote:
The CODEC I am working with takes byte-long gain value in two's complement form. In soc-core.c, the closest functions I see are snd_soc_info_volsw_s8 snd_soc_get_volsw_s8 snd_soc_set_volsw_s8
These functions are coded to work with two integer values. For my purpose, I suppose that I can always set 2nd integer input as zero. However, would I still be able to set volume like amixer sset "Codec Gain" 100 as percentage. If yes, how will amixer know to put upper 8 bits of 16 bit gain in 2nd integer value element?
Could you clarify what the control you're dealing with is? You say above that your gains are byte long but here you're talking about them actually being 16 bit. If they're 16 bit you probably need to write a new control type.
Yes, CODEC in question takes byte-long signed gain value and would like to reuse snd_soc_xxx_volsw_xx mixer callback functions in soc-core.c. The only functions I see handle signed value are snd_soc_info_volsw_s8, snd_soc_get_volsw_s8, snd_soc_get_volsw_s8 Unless I am mistaken, these functions deal with two signed byte-long values which get concatenated into 16-bit value. Perhaps, original purpose is to set left and right 8-bit gain values at the same time on a single codec register which takes 16-bit value. So, my question is whether I should reuse volsw_s8 mixer control functions and have mixer application ignore integer.value[1] to suit my purpose or redefine new set of mixer control functions i.e snd_soc_set_volsw_single_s8. Otherwise, is there existing alternative to handle set/put byte-long signed value?
Thanks Patrick
On Tue, Jun 28, 2011 at 09:21:31AM -0700, Patrick Lai wrote:
Yes, CODEC in question takes byte-long signed gain value and would like to reuse snd_soc_xxx_volsw_xx mixer callback functions in soc-core.c. The only functions I see handle signed value are snd_soc_info_volsw_s8, snd_soc_get_volsw_s8, snd_soc_get_volsw_s8 Unless I am mistaken, these functions deal with two signed byte-long values which get concatenated into 16-bit value. Perhaps, original
No, they shouldn't do that - they should handle stereo pairs in a single register. Looks like they just need a little massaging to cope with mono controls.
So, my question is whether I should reuse volsw_s8 mixer control functions and have mixer application ignore integer.value[1] to suit my purpose or redefine new set of mixer control functions i.e snd_soc_set_volsw_single_s8. Otherwise, is there existing alternative to handle set/put byte-long signed value?
Make the current controls handle mono.
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Mark Brown -
Patrick Lai