On Mon, Feb 12, 2018 at 2:39 PM, Oliver Neukum <oneukum@xxxxxxxx> wrote: > Am Sonntag, den 11.02.2018, 22:17 +0200 schrieb Ran Shalit: >> On Tue, Feb 6, 2018 at 8:55 AM, Felipe Balbi >> <felipe.balbi@xxxxxxxxxxxxxxx> wrote: >> > >> > >> > Hi, >> > >> > Ran Shalit <ranshalit@xxxxxxxxx> writes: >> > > >> > > Hello, >> > > >> > > I check code in: >> > > https://elixir.free-electrons.com/linux/v3.3/source/drivers/usb/gadget/f_mass_storage.c >> > > but I see no API usage of DMA, yet it is being mentioned as if it is used. >> > >> > but it is used. It's just managed by the UDC driver (dwc3, musb, >> > chipidea, Renesas, etc) >> > >> Just to be sure, >> can I assume that other usb gadget drivers are using DMA (including >> gadgetfs for userspace driver) ? >> And it is also correct for host drivers (such as camera device ) ? > > None of these drivers are for hardware. They implement a protocol. > On the host as well as on the gadget side there are driver for the > actual host controllers (EHCI, XHCI, ...) as well as their gadget > equivalents. > > Any of these drivers may or may not use DMA. Neither the assumption > that they use DMA or the assumption that they do not use DMA > is valid. In fact they may mix it. I asked about DMA > Your code must be ready to cope with either usage. > > HTH > Oliver > -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
