[PATCH v2] spi: add spi_tegra driver

[Erik Gilling]

On Wed, Aug 25, 2010 at 2:22 PM, Erik Gilling <konkers at android.com> wrote:
>> As an aside, and commenting on the tegra DMA api... Is the IS_ERR()
>> pattern in the tegra_dma_allocate_channel() return really a good idea
>> here?  Personally I find that pattern isn't very useful, especially
>> when the results is either "yes, allocated" or "no, not-alocated", and
>> it is very easy to write code that tests the wrong thing on the return
>> value because the compiler cannot catch it.  In other words, if it
>> isn't vital to return a specific error code, the using the PTR_ERR()
>> pattern adds unnecessary risk to the code because developers are used
>> to seeing and writing this pattern:
>>
>> tspi->rx_dma = tegra_dma_allocate_channel(TEGRA_DMA_MODE_ONESHOT);
>> if (!tspi->rx_dma)
>>        return -ENOMEM;
>>
>> The compiler won't catch it if the return value is an PTR_ERR.
>>
>> (I know that some subsystems make heavy use of it, particularly
>> filesystems and the block layer which do need to return specific error
>> codes to userspace.  My argument is that the specific error code is
>> probably irrelevant when allocating DMA channels)
>
> I don't have a strong opinion either way but that's the way Colin's
> code is written.  I'll let him speak to that.

I spoke with colin about this.  He's fine getting rid of the PTR_ERR.
I'll post a DMA and SPI patch when that's done.

-Erik