Re: [RFC PATCH 3/5] pxa: clean up the legacy SSP API - Russell King

From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Daniel Ribeiro <drwyrm@gmail.com>
Cc: alsa-devel@alsa-project.org, Eric Miao <eric.y.miao@gmail.com>,
	Mark Brown <broonie@sirena.org.uk>,
	Philipp Zabel <philipp.zabel@gmail.com>,
	Paul Shen <bshen9@marvell.com>,
	linux-arm-kernel <linux-arm-kernel@lists.arm.linux.org.uk>
Subject: Re: [RFC PATCH 3/5] pxa: clean up the legacy SSP API
Date: Wed, 29 Apr 2009 08:27:06 +0100	[thread overview]
Message-ID: <20090429072706.GA31566@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <1240959968.30410.1.camel@brutus>

On Tue, Apr 28, 2009 at 08:06:08PM -0300, Daniel Ribeiro wrote:
> Em Ter, 2009-04-28 às 23:20 +0100, Russell King - ARM Linux escreveu:
> > On Thu, Apr 23, 2009 at 01:06:12PM +0800, Eric Miao wrote:
> > > Actually, due to the number of possible SSP configurations, it's quite a
> > > difficult job to maintain an API that can be well re-used. The guideline
> > > here is to keep only a list of SSP devices and their basic information,
> > > and it's up to the user driver (like SPI or Audio SSP) to configure the
> > > SSP in a desired way.
> > 
> > Hmm, the LX battery driver uses this API for its rudimentary battery
> > communication channel with the PCON.
> > 
> > What are you suggesting as the replacement API?  Direct register access?
> 
> The SPI subsystem?

Can the SPI system cope with the other chip being the master of the
interface.  In other words, can SPI sit around primed for a transfer,
and notify the user of SPI that new data has arrived?

If not, the SPI subsystem is totally unsuitable for this.