Re: [PATCHv1 2/3] spi: Add spi driver for Socionext Synquacer platform

On Tue, Jan 09, 2018 at 07:59:05PM +0000, Trent Piepho wrote:

Usually when a device has a fifo that must be emptied before it
overflows, it is either emptied from an interrupt handler or the
interrupt handler will queue a work function or tasklet that will empty
it.  Doing it from user context has a maximum latency that is too high.

It wouldn't be the first SPI controller that lacked interrupt support,
this is depressingly common.