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From: Ryan Mallon <ryan@bluewatersys.com>
To: Thomas Chou <thomas@wytron.com.tw>
Cc: David Brownell <dbrownell@users.sourceforge.net>,
	Grant Likely <grant.likely@secretlab.ca>,
	linux-kernel@vger.kernel.org, nios2-dev@sopc.et.ntust.edu.tw,
	devicetree-discuss@lists.ozlabs.org,
	spi-devel-general@lists.sourceforge.net
Subject: Re: [PATCH v9] spi: New driver for Altera SPI
Date: Tue, 15 Feb 2011 22:12:54 +1300	[thread overview]
Message-ID: <4D5A4396.9080003@bluewatersys.com> (raw)
In-Reply-To: <4D5A2591.5090901@wytron.com.tw>

On 15/02/11 20:04, Thomas Chou wrote:
> Dear Ryan,
> 
> On 02/14/2011 10:20 AM, Ryan Mallon wrote:
>> On 02/14/2011 03:10 PM, Thomas Chou wrote:
>>> This patch adds a new SPI driver to support the Altera SOPC Builder
>>> SPI component. It uses the bitbanging library.
>>>
>>> Signed-off-by: Thomas Chou<thomas@wytron.com.tw>
>>> ---
>>
>>> +struct altera_spi {
>>> +    /* bitbang has to be first */
>>> +    struct spi_bitbang bitbang;
>>
>> Is this still true? I had a quick look and can't see anything which
>> relies on spi_bitbang being the first entry. Things like this should be
>> using container_of so that position in the struct is irrelevant.
>>
>> ~Ryan
>>
> 
> Yes, sadly true. This is due to the implementation of the bitbanging
> library, spi_bitbang.c, which assumes the struct spi_bitbang is the
> first of drvdata. Though it could be changed in the future (beyond this
> little driver), every bitbanging library user has to follow this for now.

Hmm, I see how it works now. Shouldn't the conversion be done like this:

  struct spi_bitbang *bitbang = spi_master_get_devdata(master);
  struct altera_spi *altera = container_of(bitbang,
				 struct altera_spi, bitbang);

Which doesn't require the bitbang field to be the first in the struct
and makes it more clear what is actually going on. The above could be
wrapped into a to_altera_spi macro.

~Ryan



  reply	other threads:[~2011-02-15  9:13 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-10-08  6:03 [PATCH] " Thomas Chou
2011-01-17  5:46 ` [PATCH v2] " Thomas Chou
2011-01-17  5:59   ` Stephen Rothwell
2011-01-17  6:22     ` Thomas Chou
2011-01-17  6:45       ` Grant Likely
2011-01-17  7:04         ` [PATCH v3] " Thomas Chou
2011-01-17  7:27           ` Sinan Akman
2011-01-18  1:33             ` Thomas Chou
2011-01-19  1:36             ` Thomas Chou
2011-01-17  6:56   ` [PATCH v2] " Grant Likely
2011-01-17  7:13     ` [PATCH v4] " Thomas Chou
2011-01-17  7:42       ` Grant Likely
2011-01-24  6:38         ` [PATCH v5] " Thomas Chou
2011-02-03 10:02           ` [PATCH v6] " Thomas Chou
2011-02-03 17:34             ` Grant Likely
2011-02-05 13:08               ` Thomas Chou
2011-02-05 14:02               ` [PATCH v7] " Thomas Chou
2011-02-06 20:23                 ` Peter Korsgaard
2011-02-08  2:43                   ` Thomas Chou
2011-02-08  5:21                   ` [PATCH v8] " Thomas Chou
2011-02-14  2:10                     ` [PATCH v9] " Thomas Chou
2011-02-14  2:20                       ` Ryan Mallon
2011-02-15  7:04                         ` Thomas Chou
2011-02-15  9:12                           ` Ryan Mallon [this message]
2011-02-15 19:42                           ` Grant Likely
2011-02-15 21:58                             ` Ryan Mallon
2011-02-16  2:47                       ` Grant Likely

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