On Thu, Mar 16 2017, Greg KH wrote:
> On Tue, Mar 07, 2017 at 03:09:46PM +0100, Michal Sojka wrote:
>> Since commit b65502879556 ("uio: we cannot mmap unaligned page
>> contents") addresses and sizes of UIO memory regions must be
>> page-aligned. If the address in the BAR register is not page-aligned,
>> the mentioned commit forces the UIO driver to round the address down
>> to the page size. Then, there is no easy way for user-space to learn
>> the offset of the actual memory region within the page, because the
>> offset seen in the sysfs is calculated from the rounded address and
>> thus it is always zero.
>>
>> Fix that problem by including the offset in struct uio_mem. UIO
>> drivers can set this field and its value is reported via sysfs.
>
> It is, where?
/sys/class/uio/uio0/maps/map0/offset
>>
>> Drivers for hardware with page-aligned BARs need not to be modified
>> provided that they initialize struct uio_info with zeros.
>>
>> Signed-off-by: Michal Sojka <sojk...@fel.cvut.cz>
>> ---
>> drivers/uio/uio.c | 2 +-
>> include/linux/uio_driver.h | 13 ++++++++-----
>> 2 files changed, 9 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
>> index fba021f5736a..27c329131350 100644
>> --- a/drivers/uio/uio.c
>> +++ b/drivers/uio/uio.c
>> @@ -66,7 +66,7 @@ static ssize_t map_size_show(struct uio_mem *mem, char
>> *buf)
>>
>> static ssize_t map_offset_show(struct uio_mem *mem, char *buf)
>> {
>> - return sprintf(buf, "0x%llx\n", (unsigned long long)mem->addr &
>> ~PAGE_MASK);
>> + return sprintf(buf, "0x%llx\n", (unsigned long long)mem->offs);
>
> All you changed was this value that sysfs shows.
>
>> }
>>
>> struct map_sysfs_entry {
>> diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
>> index 32c0e83d6239..89b53094f127 100644
>> --- a/include/linux/uio_driver.h
>> +++ b/include/linux/uio_driver.h
>> @@ -23,11 +23,13 @@ struct uio_map;
>> /**
>> * struct uio_mem - description of a UIO memory region
>> * @name: name of the memory region for identification
>> - * @addr: address of the device's memory (phys_addr is used since
>> - * addr can be logical, virtual, or physical & phys_addr_t
>> - * should always be large enough to handle any of the
>> - * address types)
>> - * @size: size of IO
>> + * @addr: address of the device's memory rounded to page
>> + * size (phys_addr is used since addr can be
>> + * logical, virtual, or physical & phys_addr_t
>> + * should always be large enough to handle any of
>> + * the address types)
>> + * @offs: offset of device memory within the page
>> + * @size: size of IO (multiple of page size)
>> * @memtype: type of memory addr points to
>> * @internal_addr: ioremap-ped version of addr, for driver internal use
>> * @map: for use by the UIO core only.
>> @@ -35,6 +37,7 @@ struct uio_map;
>> struct uio_mem {
>> const char *name;
>> phys_addr_t addr;
>> + unsigned long offs;;
>
> Did you really test this patch? Why the two ;;? And who sets this?
>
> I think you broke things :(
This is set in patch 3/3 and it works correctly on my hardware. It seems
like you would like to have patches 2/3 and 3/3 merged in a single one.
I'll send v2 in a while and address your other comments as well.
Thanks.
-Michal
