Re: [patch 2.6.28-rc9] spi: spi_write_then_read() regression fix

[David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>]

On Wednesday 24 December 2008, Baruch Siach wrote:
> > I've certainly seen a couple drivers that handled the
> > full duplex behavior incorrectly, until they fixed that
> > bug.  As in, they wrote the tx_buf *then* read rx_buf
> > (a half-duplex model) instead of doing them concurrently
> > (the full-duplex model a spi_master must implement).
> 
> May you name those drivers and the commits with the bug fixes?
> I couldn't find them in Linus' tree.

I don't recall such a driver merging to mainline;
the idea is to catch such fundamental bugs before
they merge.


> I'm working on an SPI master (DesignWare) driver and I want
> to make sure that  I'm implementing the API correctly.

Lacking a test suite for the spi_master drivers,
I suggest that you verify your driver works with
some of the existing protocol drivers.  If at all
possible, hook up a couple SPI slaves to different
chipselects on your master, and test them all.

Then, if you find misbehavior when you test a
driver that's already known to work with a bunch
of controller drivers, it's more likely that the
bug is in your new code than the existing code.

- Dave





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