Re: [PATCH 6/7] soundwire: debugfs: add interface to read/write commands

[Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>]

On 4/5/24 06:45, Vinod Koul wrote:
> On 26-03-24, 09:01, Bard Liao wrote:
>> From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
>>
>> We have an existing debugfs files to read standard registers
>> (DP0/SCP/DPn).
>>
>> This patch provides a more generic interface to ANY set of read/write
>> contiguous registers in a peripheral device. In follow-up patches,
>> this interface will be extended to use BRA transfers.
>>
>> The sequence is to use the following files added under the existing
>> debugsfs directory for each peripheral device:
>>
>> command (write 0, read 1)
>> num_bytes
>> start_address
>> firmware_file (only for writes)
>> read_buffer (only for reads)
>>
>> Example for a read command - this checks the 6 bytes used for
>> enumeration.
>>
>> cd /sys/kernel/debug/soundwire/master-0-0/sdw\:0\:025d\:0711\:01/
>> echo 1 > command
>> echo 6 > num_bytes
>> echo 0x50 > start_address
>> echo 1 > go
> 
> can we have a simpler interface? i am not a big fan of this kind of
> structure for debugging.
> 
> How about two files read_bytes and write_bytes where you read/write
> bytes.
> 
> echo 0x50 6 > read_bytes
> cat read_bytes
> 
> in this format I would like to see addr and values (not need to print
> address /value words (regmap does that too)
> 
> For write
> 
> echo start_addr N byte0 byte 1 ... byte N > write_bytes

I think you missed the required extension where we will add a new
'command_type' to specify which of the regular or BTP/BRA accesses is used.

Also the bytes can come from a firmware file, it would be very odd to
have a command line with 32k value, wouldn't it?

I share your concern about making the interface as simple as possible,
but I don't see how it can be made simpler really. We have to specify
- read/write
- access type (BRA or regular)
- start address
- number of bytes
- a firmware file for writes
- a means to see the read data.

And I personally prefer one 1:1 mapping between setting and debugfs
file, rather than a M:1 mapping that require users to think about the
syntax and which value maps to what setting. At my age I have to define
things that I will remember on the next Monday.