Re: [PATCH v4 06/10] ARM: defconfig: Use the new FSL QSPI driver under the SPI framework

[Boris Brezillon <boris.brezillon@xxxxxxxxxxx>]

On Wed, 7 Nov 2018 16:36:13 +0000
Schrempf Frieder <frieder.schrempf@xxxxxxxxxx> wrote:

> Hi Olof,
> 
> On 07.11.18 17:20, Olof Johansson wrote:
> > On Wed, Nov 7, 2018 at 6:44 AM Frieder Schrempf
> > <frieder.schrempf@xxxxxxxxxx> wrote:  
> >>
> >> From: Frieder Schrempf <frieder.schrempf@xxxxxxxxx>
> >>
> >> The new driver at spi/spi-fsl-qspi.c replaces the old SPI NOR driver
> >> at mtd/fsl-quadspi.c. Switch to the new driver in the defconfigs.
> >>
> >> Signed-off-by: Frieder Schrempf <frieder.schrempf@xxxxxxxxx>  
> > 
> > Hi Frieder,
> > 
> > This patch is part of a series that I didn't see the rest of, but in
> > general we prefer to merge these through arm-soc even if the driver
> > goes in through another tree. The way we'd prefer to handle it is that
> > once the driver lands, we'll take the config option change to turn it
> > on. To avoid our branches to break until both sides have landed, it
> > might be a good idea to keep both drivers on for a short while (one
> > release).
> > 
> > So, I'm not going to ack this since we avoid taking defconfig changes
> > through driver trees (these two defconfigs tend to churn a lot and we
> > don't want to create merge conflicts where we don't have to), but
> > we'll be happy to pick it up when the time comes.  
> 
> Ok, thank you for explaining the common practice. I will drop the config 
> changes for the next version and send it separately when the time is ready.
> 
> Both the old driver and the new one use the same compatible strings for 
> probing. Wouldn't that cause problems if both drivers are enabled for a 
> while, or am I missing something?

Or maybe we should not introduce a new Kconfig option and just reuse
the old one. It probably requires re-ordering patches a bit (patch 1
should be moved after patch 5). Then you have 2 choices:

1/ merge patch 1 and 6 so that the new driver effectively replaces the
   old one but uses the same Kconfig option
2/ remove the ability to compile the old driver when the new one is
   introduced: remove the line from drivers/mtd/spi-nor Makefile and
   move the Kconfig entry from drivers/mtd/spi-nor/Kconfig to
   drivers/spi/Kconfig. And remove the old code in a separate patch

I'm fine either way, but option #2 will probably make the patch
introducing the new driver bigger and hurt readability.