On Mon, May 18, 2009 at 6:50 AM, Grant Grundler <grundler@xxxxxxxxxxxxxxxx> wrote: > Hi Arun, Sandeep, > > On Sat, May 16, 2009 at 06:33:44PM +0530, SandeepKsinha wrote: >> Hi Arun, >> >> On Sat, May 16, 2009 at 5:48 PM, arun c <arun.edarath@xxxxxxxxx> wrote: >> > Hi all, >> > >> > I want to copy data from user space to PCI memory. >> > >> > I mapped the PCI memory of the card by, >> > >> > 1)pci_request_regions(pci_dev, DEVICE_NAME); >> > 2)buffer_addr = pci_iomap(pci_dev, 1, 1024); >> > >> > Now I want to write data supplied by the >> > user to buffer_addr(BAR1 pre-fetch-able memory >> > of the device) >> > >> > I did like this: >> > >> > copy_from_user(buffer_addr, usr_addr, 1024) >> > >> > This method is working fine on an X86 running >> > linux 2.6.27 kernel. I can see the data clearly copied. >> > >> > I want to know is this legal for all the platforms? and for >> > older kernels starting from 2.6.16? >> > >> > If the above method is totally legal then can I use >> > copy_to_user(usr_addr, buffer_addr, 1024) also? >> >> AFAIK, yes. > > Sorry, I don't think so. > > Copying stuff to non-cacheable addresses can have other side effects. > So the optimizations available when copying TO cacheable address space > are generally not available (or have risks). > I totally agree with this. > That's why we have copy_from_user_toio() > http://www.digipedia.pl/man/copy_from_user_toio.9.html > Remember that there are various flavours of it and each one has its own specific use. Arun's question was not very specific to a situation, it was generic. If needed, he can always look at the other flavours of copy_to/from_user. . > hth, > grant > -- Regards, Sandeep. “To learn is to change. Education is a process that changes the learner.” -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
