On Tue, Oct 15, 2013 at 11:01 AM, Brian Norris <[email protected]> wrote: >> So, the flow can be something like this: >> >> drivers/mtd/devices/m25p80.c >> get_flash_buf() >> { >> lock(); >> >> t[0] = GET_BUFFER; >> t[1] = buf; >> ...... >> >> spi_sync(); >> >> unlock(); >> } >> >> mtd_read >> { >> get_flash_buf(); >> >> if (flash->buf) { >> memcpy(); >> return 0; >> } >> } >> >> Not sure, if free buf is needed as devm_* variant is used to allocate that >> memory. > > I believe you are misplacing the discussion of devm_* variants. devm_* > is only useful for resources allocated/mapped released/unmapped at probe > and release time. They do not magically remove the burden of resource > management for I/O and other dynamic operations.
Are there any numbers to show if memory mapped read support is a benefit in Linux? There is some question as to whether it's useful at all or not. If it is, I think low latency for small reads is probably one of the only advantages. To do that, you aren't going to want to deal with device PM for every single read. It would make more sense to turn the hardware on when the MTD device is opened and leave it on until closed. ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60135031&iu=/4140/ostg.clktrk _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
