Re: [PATCH v2 3/4] spi: Split transfers larger than max size

[Eddie James <eajames@linux.ibm.com>]

On 9/27/22 06:21, Vincent Whitchurch wrote:
> A couple of drivers call spi_split_transfers_maxsize() from their
> ->prepare_message() callbacks to split transfers which are too big for
> them to handle.  Add support in the core to do this based on
> ->max_transfer_size() to avoid code duplication.


Hello,

I've been testing AT25 functionality in linux 6.1 and I believe this 
patch is breaking the AT25 protocol. It will split a write command up 
such that some of the data is in a different transfer than  the write 
enable and address. According to my understanding of the AT25 spec, that 
doesn't work... Someone correct me if I'm wrong though. Do we need a 
flag to enable/disable this behavior depending on the client perhaps?


Thanks,

Eddie


>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
> ---
>   drivers/spi/spi.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index f41a8c2752b8..44e4352d948b 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1649,6 +1649,15 @@ static int __spi_pump_transfer_message(struct spi_controller *ctlr,
>   
>   	trace_spi_message_start(msg);
>   
> +	ret = spi_split_transfers_maxsize(ctlr, msg,
> +					  spi_max_transfer_size(msg->spi),
> +					  GFP_KERNEL | GFP_DMA);
> +	if (ret) {
> +		msg->status = ret;
> +		spi_finalize_current_message(ctlr);
> +		return ret;
> +	}
> +
>   	if (ctlr->prepare_message) {
>   		ret = ctlr->prepare_message(ctlr, msg);
>   		if (ret) {