Re: [PATCH v3 net-next 1/2] net: dsa: sja1105: send multiple spi_messages instead of using cs_change

On Mon, May 24, 2021 at 09:35:29AM +0100, Mark Brown wrote:

On Fri, May 21, 2021 at 12:16:56AM +0300, Vladimir Oltean wrote:

quoted

The fact of the matter is that spi_max_message_size() has an ambiguous
meaning if any non-final transfer has cs_change = true.

This is not the case, spi_message_max_size() is a limit on the size of a
spi_message.

That is true, although it doesn't mean much, since in the presence of
cs_change, a spi_message has no correspondent in the physical world
(i.e. you can't look at a logic analyzer dump and say "this spi_message
was from this to this point"), and that is the problem really.
Describing the controller's inability to send more than N SPI words with
continuous chip select using spi_message_max_size() is what seems flawed
to me, but it's what we have, and what I've adapted to.