On 03/29/2014 03:30 AM, Songhee Baek wrote:
-----Original Message----- From: Songhee Baek Sent: Friday, March 28, 2014 11:10 AM To: 'Lars-Peter Clausen' Cc: Arun Shamanna Lakshmi; 'lgirdwood@gmail.com'; 'broonie@kernel.org'; 'swarren@wwwdotorg.org'; 'alsa-devel@alsa-project.org'; 'tiwai@suse.de'; 'linux-kernel@vger.kernel.org' Subject: RE: [alsa-devel] [PATCH] ASoC: Add support for multi register mux
On 03/26/2014 11:41 PM, Songhee Baek wrote:
On 03/26/2014 01:02 AM, Arun Shamanna Lakshmi wrote:
The way you describe this it seems to me that a value array for this kind of mux would look like.
0x00000000, 0x00000000, 0x00000001 0x00000000, 0x00000000, 0x00000002 0x00000000, 0x00000000, 0x00000003 0x00000000, 0x00000000, 0x00000004 0x00000000, 0x00000000, 0x00000008 ...
That seems to be extremely tedious. If the MUX uses a one hot encoding how about storing the index of the bit in the values array and use (1 << value) when writing the value to the register?
If we store the index of the bit, the value will be duplicated for each
registers inputs since register has 0 to 31bits to shift, then we need to decode the index to interpret value for which registers to set. If we need to interpret the decoded value of index, it is better to have custom put/get function in our driver, isn't it?
I'm not sure I understand. If you use (val / 32) to pick the register and (val % 32) to pick the bit in the register this should work just fine. Maybe I'm missing something. Do you have a real world code example of of the this type of enum is used?
I can use val/32 and val%32 for this multi register mux.
With this logic, put function would be easy however get function becomes tedious due to looping on each bit per register for 3 of them in our case. Rather, it would be easy to identify a unique MUX_OFFSET to distinguish between the 3 registers as shown in the code below.
I'm not sure I understand how that MUX_OFFSET would work. To get the selected mux output you can use the ffs instruction.
foreach(reg) { reg_val = read(reg) & mask; if (reg_val != 0) { val = __ffs(reg_val); break; } }
- Lars