Hi Bart,
> -----Original Message-----
> From: [email protected] [mailto:linux-rdma-
> [email protected]] On Behalf Of Bart Van Assche
> Sent: Monday, March 6, 2017 6:36 PM
> To: Doug Ledford <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>; Sebastian Ott
> <[email protected]>; Parav Pandit <[email protected]>; linux-
> [email protected]; [email protected]; Bart Van Assche
> <[email protected]>; Bjorn Helgaas <[email protected]>;
> Benjamin Herrenschmidt <[email protected]>; David Woodhouse
> <[email protected]>; H . Peter Anvin <[email protected]>; Ingo Molnar
> <[email protected]>; Russell King <[email protected]>
> Subject: [PATCH 1/2] device: Stop requiring that struct device is embedded in
> struct pci_dev
>
> The dma mapping operations of several architectures and also of several I/O
> MMU implementations need to translate a struct device pointer into a struct
> pci_dev pointer. This translation is performed by to_pci_dev(). That macro
> assumes that struct device is embedded in struct pci_dev. However, that is
> not the case for the device structure in struct ib_device. Since that device
Why can't ib subsystem pass device structure that is embedded in pci_dev when
it makes calls to dma_map APIs?
The whole point of clean up was to avoid an if() condition in hot datapath.
If we invoke dma_map_ and friend functions with right device, shouldn't it work?
That avoids the if() condition as well and avoids changing core of Linux like
done in this bug fix.
I think ib_device should store the right struct device pointer that needs to go
to dma_apis, rather than including pci_dev structure pointer in device core
layer.
Pseudo example code:
struct ib_device {
struct device *dma_device;
};
ib_dma_unmap_single() which had if(), that got removed with dma_unmap_single()
with cleanup patch.
Instead of,
static inline void ib_dma_unmap_single(struct ib_device *dev,
u64 addr, size_t size,
enum dma_data_direction direction)
{
dma_unmap_single(&dev->dev, addr, size, direction);
}
Why can't we do this?
static inline void ib_dma_unmap_single(struct ib_device *dev,
u64 addr, size_t size,
enum dma_data_direction direction)
{
dma_unmap_single(dev->dma_device, addr, size, direction);
}
This avoids increasing all device size by 8 bytes in system.
It also clean approach where core device structure doesn't have to bother for
pci_dev.
