Le 28/02/2022 à 17:14, Mark Brown a écrit : > On Mon, Feb 28, 2022 at 04:02:30PM +0000, Christophe Leroy wrote: >> Le 28/02/2022 à 16:29, Mark Brown a écrit : > >>> The binding looks good now but this is still driver specific code when >>> it looks like it could easily be implemented in the core - like I said >>> on the previous version you'd need to update drivers to advertise less >>> than 8 bits but there's basically nothing driver specific I can see here >>> so any driver using transfer_one() would get support that way. > >> Argh ! Sorry your comment to the previous version ended up in Junk >> mails. I see it now. > > No problem. > >> We discussed that back in 2016 in >> https://lore.kernel.org/linux-spi/20160824112701.GE22076@xxxxxxxxxxxxx/ >> and my understanding at that time was that it was not something that >> could be done at core level. > >> But maybe things have changed since then ? > > What I said then was "it would need a new core feature" which is what > the binding does, I'm suggesting that you also do that for the handling > of the implementation as well. > > Actually now I think about it perhaps this shouldn't be a binding at all > but rather something specified by the client driver - presumably any > system using an affected device is going to need these extra clock > cycles so they'll all need to add the same property. > >> By the way, fsl-spi driver doesn't implement transfer_one() but >> transfer_one_message() so it takes care of the chipselect changes and >> therefore the final dummy transfer with CS off is to be done there as >> far as I understand. > >> Would it mean changing fsl-spi driver to implement transfer_one() first ? > > Well, if it can implement transfer_one() without any negative > consequences whichh Seems like your sentence is truncated. My understanding today is that this trailing transfer with chipselect OFF is to be added at the end of transfer_one_message(). It can be implemented in the core transfer_one_message() for drivers implementing transfer_one(). For the other drivers not having transfer_one() but having transfer_one_message(), it must be implemented in the driver's transfer_one_message(). Am I right ? fsl-spi driver is the one I need to support this new functionnality and it has its own transfer_one_message(). What would you expect ? Thanks Christophe
