On Thu, Feb 15, 2018 at 10:56 AM, Ran Shalit <ranshalit@xxxxxxxxx> wrote: > 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. > Hi, I actually asked about DMA, because I see that it is possible to send urb using DMA allocated buffers or not (coherent and non-coherent) usb_buffer_alloc(). So, How can we actually know if I should use this API with a device or not ? I mean, is it always possible to use the coherent buffer with the device ? Sorry for the previous disrupted email, it was sent by mistake. Thanks a lot, Ran that there is API for 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
