Re: [PATCH] spi: add driver for BCM2835

From: Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
To: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
Cc: Grant Likely
	<grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>,
	spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
	Chris Boot <bootc-1Slo4GeK4H1eoWH0uzbU5w@public.gmane.org>,
	linux-rpi-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [PATCH] spi: add driver for BCM2835
Date: Tue, 12 Mar 2013 19:06:38 +0000	[thread overview]
Message-ID: <20130312190638.GA19942@opensource.wolfsonmicro.com> (raw)
In-Reply-To: <5139815E.7020502-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>

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On Thu, Mar 07, 2013 at 11:12:46PM -0700, Stephen Warren wrote:
> On 03/05/2013 09:05 PM, Mark Brown wrote:
> > On Tue, Mar 05, 2013 at 07:49:02PM -0700, Stephen Warren wrote:
> 
> >> +	switch (bpw) { +	case 8: +		break; +	default: +
> >> dev_err(&spi->dev, "unsupported bits_per_word=%d\n", bpw); +
> >> return -EINVAL; +	}

> Is there an assumption in the SPI core that bpw will never be >32? The
> value is stored in a u8 in the controller and transfer structs, so
> large values are physically possible. So if there is no such
> assumption, then representing all of an SPI controller's supported BPW
> in a mask/list would be a little unwieldy, so doing central checking
> might not work well.

I don't think there's such an assumption, on the other hand such
hardware is exceptionally rare so it seems sensible to at least handle
the common case - for example, allow the driver to specify a bitmask and
if no mask is specified just accept anything and let the drive worry
about it.

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