linux-kernel - Re: [PATCH v2 0/2] eeprom: at25: SPI transfer improvements

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Date:   Wed, 30 Jan 2019 15:55:43 +0100
From:   Boris Brezillon <bbrezillon@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        MTD Maling List <linux-mtd@...ts.infradead.org>,
        Nguyen An Hoan <na-hoan@...so.co.jp>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] eeprom: at25: SPI transfer improvements

On Tue, 29 Jan 2019 20:02:37 +0100
Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> Hi Boris,
> 
> On Fri, Jan 18, 2019 at 11:07 PM Boris Brezillon <bbrezillon@...nel.org> wrote:
> > Did you consider converting this driver to spimem? Looks like the
> > protocol used to communicate with the memory resembles the one used on
> > SPI NANDs/NORs and fits pretty well in the spi_mem_op representation.
> >
> > By doing this conversion you'd allow people to connect an AT25 EEPROM
> > to an advanced SPI controller that does not support regular SPI
> > transfers and you wouldn't have to forge SPI messages manually.
> >
> > Here is a patch (only compile tested) doing that. The diffstat is not in
> > favor of this conversion, but I find the resulting code cleaner and more
> > future proof.  
> 
> Thanks, seems to work fine, with the 512-byte 25LC040 I have!
> 
> Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>
> 
> I did notice that the first two-byte transfer (command+offset) of each
> message is now split in two one-byte transfers, though.

That's something we can optimize in drivers/spi/spi-mem.c if you think
it makes a difference.