Thanks for the inputs
On 10/03/2020 15:53, Pierre-Louis Bossart wrote:
Hi Srinivas,
> My recommendation would be to add a DisCo property stating the WordLength value can be used by the bus code but not written to the Slave device registers.
Does something like "mipi-sdw-read-only-wordlength" as slave property, make sense?
The properties can be handled at two levels.
First, you'd want to change include/linux/soundwire/sdw.h, and add a new field in
struct sdw_dpn_prop { u32 num; u32 max_word; u32 min_word; u32 num_words; u32 *words; + bool read_only_wordlength;
Once this is added, along with the code that bypasses the programming of DPn_BlockCtrl1, the implementation has two choices:
a) hard-code the field value in the codec driver.
This totally works for me.
b) read the property from firmware with the DisCo helpers.
I would defer adding this for now till there is a real users for this.
There is no requirement that all properties be read from firmware, and if you look at existing code base sdw_slave_read_prop() is currently unused, each codec implements its own .read_prop() callback.
We really wanted to be pragmatic, and give the possibility to either override bad firmware or extend incomplete firmware to avoid coupling OS and firmware too much. If you foresee cases where this implementation might vary and firmware distribution is not a problem, then a property read would make sense.
Just once procedural reminder that all 'mipi-sdw' properties are handled by the MIPI software WG, so we'd need to have this property added in a formal MIPI document update.
I suggest you talk with Lior first on this.
Sure, I will talk to him.
Hope this helps -Pierre