From mboxrd@z Thu Jan 1 00:00:00 1970 From: geert@linux-m68k.org (Geert Uytterhoeven) Date: Thu, 8 Dec 2016 12:59:54 +0100 Subject: Tearing down DMA transfer setup after DMA client has finished In-Reply-To: References: <58356EA8.2010806@free.fr> <20161125045549.GC2698@localhost> <092f44ee-4560-be17-25f7-00948dba3cfa@free.fr> <20fc9020-7278-bc2f-2a8d-43aff5cabff8@free.fr> <20161206051222.GQ6408@localhost> <5846B237.8060409@free.fr> <20161207164341.GX6408@localhost> <20161208103921.GC6408@localhost> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Dec 8, 2016 at 12:44 PM, M?ns Rullg?rd wrote: > Vinod Koul writes: >> On Wed, Dec 07, 2016 at 04:45:58PM +0000, M?ns Rullg?rd wrote: >>> Vinod Koul writes: >>> > On Tue, Dec 06, 2016 at 01:14:20PM +0000, M?ns Rullg?rd wrote: >>> >> That's not going to work very well. Device drivers typically request >>> >> dma channels in their probe functions or when the device is opened. >>> >> This means that reserving one of the few channels there will inevitably >>> >> make some other device fail to operate. >>> > >>> > No that doesnt make sense at all, you should get a channel only when you >>> > want to use it and not in probe! >>> >>> Tell that to just about every single driver ever written. >> >> Not really, few do yes which is wrong but not _all_ do that. > > Every driver I ever looked at does. Name one you consider "correct." I'm far from claiming that drivers/tty/serial/sh-sci.c is perfect, but it does request DMA channels at open time, not at probe time. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds