[PATCH] spi-nor: sfdp: Allow configuring unknown flashes using SFDP

[Pratyush Yadav]

On 27/05/21 07:22PM, Vignesh Raghavendra wrote:
> 
> 
> On 5/21/21 5:23 PM, Petr Malat wrote:
> > Hi!
> > On Fri, May 21, 2021 at 03:25:05PM +0530, Pratyush Yadav wrote:
> >> On 20/05/21 06:07PM, Petr Malat wrote:
> >>> This change allows adding a support for flashes with correct SFDP
> >>> without recompilation of the kernel by setting sfdp-compatible property
> >>> in their node. Alternatively, sfdp_compatible module option can be used
> >>> to list JEDEC IDs of flashes, whose SFDP can be trusted. Star "*" can
> >>> be used to match all JEDEC IDs.
> >>
> >> I have skimmed through the patch. Before I look at it more closely, I 
> >> want to understand the use case for this patch. Why would you not want 
> >> to recompile the kernel when adding support for new hardware? Do you 
> >> want the ability to support flashes on devices that have already been 
> >> deployed in the field? Is it something that comes up frequently?
> > In my case the kernel is loaded from a USB mass storage device, which
> > can be preproduced and on stock (with the kernel already on it). With
> > my patch I can change the flash vendor without the need of updating
> > the image on already existing USB mass storage devices.
> > 
> > The patch is also useful for people who use distribution kernel as they
> > will not have to wait until (and if) the distribution updates it.
> 
> Don't need separate DT property or cmdline argument. There is no way to
> know if the SFDP tables are 100% valid when kernel is working with a
> "generic flash".
> Flashes are often replaced with newer revisions of the part that may/may
> not have valid SFDP tables.
> 
> So just rely on SFDP, when no valid entry is found in the manufacturer's
> flash_info[] while printing out a warning to user that this is just best
> effort support.

+1

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.