Hi Greg,
Thanks for the comments.
On Tue, 2019-02-26 at 03:53:11 -0800, Greg Kroah-Hartman wrote:
> On Sat, Feb 23, 2019 at 12:28:17PM -0800, Hyun Kwon wrote:
> > Add the dmabuf map / unmap interfaces. This allows the user driver
> > to be able to import the external dmabuf and use it from user space.
> >
> > Signed-off-by: Hyun Kwon <hyun.kwon@xxxxxxxxxx>
> > ---
> > drivers/uio/Makefile | 2 +-
> > drivers/uio/uio.c | 43 +++++++++
> > drivers/uio/uio_dmabuf.c | 210 +++++++++++++++++++++++++++++++++++++++++++
> > drivers/uio/uio_dmabuf.h | 26 ++++++
> > include/uapi/linux/uio/uio.h | 33 +++++++
> > 5 files changed, 313 insertions(+), 1 deletion(-)
> > create mode 100644 drivers/uio/uio_dmabuf.c
> > create mode 100644 drivers/uio/uio_dmabuf.h
> > create mode 100644 include/uapi/linux/uio/uio.h
> >
> > diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
> > index c285dd2..5da16c7 100644
> > --- a/drivers/uio/Makefile
> > +++ b/drivers/uio/Makefile
> > @@ -1,5 +1,5 @@
> > # SPDX-License-Identifier: GPL-2.0
> > -obj-$(CONFIG_UIO) += uio.o
> > +obj-$(CONFIG_UIO) += uio.o uio_dmabuf.o
> > obj-$(CONFIG_UIO_CIF) += uio_cif.o
> > obj-$(CONFIG_UIO_PDRV_GENIRQ) += uio_pdrv_genirq.o
> > obj-$(CONFIG_UIO_DMEM_GENIRQ) += uio_dmem_genirq.o
> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> > index 1313422..6841f98 100644
> > --- a/drivers/uio/uio.c
> > +++ b/drivers/uio/uio.c
> > @@ -24,6 +24,12 @@
> > #include <linux/kobject.h>
> > #include <linux/cdev.h>
> > #include <linux/uio_driver.h>
> > +#include <linux/list.h>
> > +#include <linux/mutex.h>
> > +
> > +#include <uapi/linux/uio/uio.h>
> > +
> > +#include "uio_dmabuf.h"
> >
> > #define UIO_MAX_DEVICES (1U << MINORBITS)
> >
> > @@ -454,6 +460,8 @@ static irqreturn_t uio_interrupt(int irq, void *dev_id)
> > struct uio_listener {
> > struct uio_device *dev;
> > s32 event_count;
> > + struct list_head dbufs;
> > + struct mutex dbufs_lock; /* protect @dbufs */
> > };
> >
> > static int uio_open(struct inode *inode, struct file *filep)
> > @@ -500,6 +508,9 @@ static int uio_open(struct inode *inode, struct file *filep)
> > if (ret)
> > goto err_infoopen;
> >
> > + INIT_LIST_HEAD(&listener->dbufs);
> > + mutex_init(&listener->dbufs_lock);
> > +
> > return 0;
> >
> > err_infoopen:
> > @@ -529,6 +540,10 @@ static int uio_release(struct inode *inode, struct file *filep)
> > struct uio_listener *listener = filep->private_data;
> > struct uio_device *idev = listener->dev;
> >
> > + ret = uio_dmabuf_cleanup(idev, &listener->dbufs, &listener->dbufs_lock);
> > + if (ret)
> > + dev_err(&idev->dev, "failed to clean up the dma bufs\n");
> > +
> > mutex_lock(&idev->info_lock);
> > if (idev->info && idev->info->release)
> > ret = idev->info->release(idev->info, inode);
> > @@ -652,6 +667,33 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
> > return retval ? retval : sizeof(s32);
> > }
> >
> > +static long uio_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>
> We have resisted adding a uio ioctl for a long time, can't you do this
> through sysfs somehow?
>
The dmabuf is managed as per process resource, so it's hard to do it through
sysfs.
> A meta-comment about your ioctl structure:
>
> > +#define UIO_DMABUF_DIR_BIDIR 1
> > +#define UIO_DMABUF_DIR_TO_DEV 2
> > +#define UIO_DMABUF_DIR_FROM_DEV 3
> > +#define UIO_DMABUF_DIR_NONE 4
>
> enumerated type?
>
> > +
> > +struct uio_dmabuf_args {
> > + __s32 dbuf_fd;
> > + __u64 dma_addr;
> > + __u64 size;
> > + __u32 dir;
>
> Why the odd alignment? Are you sure this is the best packing for such a
> structure?
>
> Why is dbuf_fd __s32? dir can be __u8, right?
The dmabuf fd is defined as int, so __s32 seems correct. Please let me know
otherwise. The dir can be __u8. Will fix if there is v2 at all.
>
> I don't know that dma layer very well, it would be good to get some
> review from others to see if this really is even a viable thing to do.
> The fd handling seems a bit "odd" here, but maybe I just do not
> understand it.
Agreed. So I'm looking forward to feedback or if there's more sensible
alternative.
Thanks,
-hyun
>
> thanks,
>
> greg k-h
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