On Thu, May 06, 2010 at 02:46:04PM -0400, Mike Frysinger wrote:
> On Thu, May 6, 2010 at 06:37, Oskar Schirmer wrote:
> > struct ser_req {
> > + u16 sample;
> > + char __padalign[L1_CACHE_BYTES - sizeof(u16)];
> > +
> > u16 reset;
> > u16 ref_on;
> > u16 command;
> > - u16 sample;
> > struct spi_message msg;
> > struct spi_transfer xfer[6];
> > };
>
> are you sure this is necessary ? ser_req is only ever used with
> spi_sync() and it's allocated/released on the fly, so how could
> anything be reading that memory between the start of the transmission
> and the return to adi7877 ?
The master driver can. atmel_spi flushes the cache of the buffers
pretty early when queuing a message and touches the message members
afterwards.
> > struct ad7877 {
> > + u16 conversion_data[AD7877_NR_SENSE];
> > + char __padalign[L1_CACHE_BYTES
> > + - AD7877_NR_SENSE * sizeof(u16)];
> > +
> > struct input_dev *input;
> > char phys[32];
> >
> > @@ -182,8 +188,6 @@ struct ad7877 {
> > u8 averaging;
> > u8 pen_down_acc_interval;
> >
> > - u16 conversion_data[AD7877_NR_SENSE];
> > -
> > struct spi_transfer xfer[AD7877_NR_SENSE + 2];
> > struct spi_message msg;
>
> i can see the spi_message inside of this struct being a problem
> because the spi transfer is doing asynchronously with spi_async().
> however, i would add a comment right above these two fields with a
> short explanation as to why they're at the start and why the pad
> exists so someone down the line doesnt move it.
Good idea.
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