Re: [PATCH v5 12/13] spi: mxic: Use spi_mem_generic_supports_op()

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Mark Brown <broonie@kernel.org>
Cc: Boris Brezillon <boris.brezillon@collabora.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Tudor Ambarus <Tudor.Ambarus@microchip.com>,
	Pratyush Yadav <p.yadav@ti.com>, Michael Walle <michael@walle.cc>,
	linux-mtd@lists.infradead.org, linux-spi@vger.kernel.org,
	Julien Su <juliensu@mxic.com.tw>,
	Jaime Liao <jaimeliao@mxic.com.tw>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Xiangsheng Hou <xiangsheng.hou@mediatek.com>
Subject: Re: [PATCH v5 12/13] spi: mxic: Use spi_mem_generic_supports_op()
Date: Thu, 16 Dec 2021 10:01:47 +0100	[thread overview]
Message-ID: <20211216100147.46c307ff@xps13> (raw)
In-Reply-To: <Ybo/r8neydqTxN6N@sirena.org.uk>

Hi Mark,

broonie@kernel.org wrote on Wed, 15 Dec 2021 19:19:11 +0000:

> On Wed, Dec 15, 2021 at 08:05:48PM +0100, Boris Brezillon wrote:
> 
> > There's also a second option that doesn't involve patching existing
> > users: add a spi_mem_controller_caps to the spi_controller struct, and
> > check this instance in your spi_mem_default_supports_op()
> > implementation. Note that the buswidth check done in the generic
> > helper is already based on caps exposed by the controller
> > through spi_controller.mode_bits ({RX/TX}_{DUAL,QUAD,OCTAL} bits).  
> 
> This approach is quite nice for things like this - having things as data
> rather than code.  The only issue is if any of the caps end up varying
> by operation and we need different capabilities but that doesn't look
> too likely here I think?

Indeed that was the main point of the original review from Boris, the
capabilities should be fixed on the controller's lifetime. So I believe
we are safe.

I think I am going to propose the following:
	const struct spi_controller_mem_ops *mem_ops;
+	struct spi_controller_mem_caps mem_caps;

As the structure is not supposed to enlarge dramatically in the near
future, I guess it's fine to have it defined statically. Please tell me
if you prefer a *mem_caps pointer.

I'll send a proposal soon.

Thanks,
Miquèl