[src/trunk]: src/sys/external/bsd/drm2/linux drm: Teach dmabuf to handle lseek.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/aec878bf15bc
branches:  trunk
changeset: 373606:aec878bf15bc
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Feb 21 11:40:13 2023 +0000

description:
drm: Teach dmabuf to handle lseek.

Needed by libdrm_amdgpu.

Based on patch from Jeff Frasca -- thanks!

XXX pullup-10

diffstat:

 sys/external/bsd/drm2/linux/linux_dma_buf.c |  58 ++++++++++++++++++++++++++++-
 1 files changed, 56 insertions(+), 2 deletions(-)

diffs (90 lines):

diff -r 463a8129fe28 -r aec878bf15bc sys/external/bsd/drm2/linux/linux_dma_buf.c
--- a/sys/external/bsd/drm2/linux/linux_dma_buf.c       Tue Feb 21 11:40:00 2023 +0000
+++ b/sys/external/bsd/drm2/linux/linux_dma_buf.c       Tue Feb 21 11:40:13 2023 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: linux_dma_buf.c,v 1.15 2022/04/09 23:44:44 riastradh Exp $     */
+/*     $NetBSD: linux_dma_buf.c,v 1.16 2023/02/21 11:40:13 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: linux_dma_buf.c,v 1.15 2022/04/09 23:44:44 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: linux_dma_buf.c,v 1.16 2023/02/21 11:40:13 riastradh Exp $");
 
 #include <sys/types.h>
 #include <sys/atomic.h>
@@ -48,6 +48,8 @@
 static int     dmabuf_fop_kqfilter(struct file *, struct knote *);
 static int     dmabuf_fop_mmap(struct file *, off_t *, size_t, int, int *,
                    int *, struct uvm_object **, int *);
+static int     dmabuf_fop_seek(struct file *fp, off_t delta, int whence,
+                   off_t *newoffp, int flags);
 
 static const struct fileops dmabuf_fileops = {
        .fo_name = "dmabuf",
@@ -61,6 +63,7 @@
        .fo_kqfilter = dmabuf_fop_kqfilter,
        .fo_restart = fnullop_restart,
        .fo_mmap = dmabuf_fop_mmap,
+       .fo_seek = dmabuf_fop_seek,
 };
 
 struct dma_buf *
@@ -288,3 +291,54 @@
        return dmabuf->ops->mmap(dmabuf, offp, size, prot, flagsp, advicep,
            uobjp, maxprotp);
 }
+
+/*
+ * We don't actually do anything with the file offset; this is just how
+ * libdrm_amdgpu expects to find the size of the DMA buf.  (Why it
+ * doesn't use fstat is unclear, but it doesn't really matter.)
+ */
+static int
+dmabuf_fop_seek(struct file *fp, off_t delta, int whence, off_t *newoffp,
+    int flags)
+{
+       const off_t OFF_MAX = __type_max(off_t);
+       struct dma_buf *dmabuf = fp->f_data;
+       off_t base, newoff;
+       int error;
+
+       mutex_enter(&fp->f_lock);
+
+       switch (whence) {
+       case SEEK_CUR:
+               base = fp->f_offset;
+               break;
+       case SEEK_END:
+               base = dmabuf->size;
+               break;
+       case SEEK_SET:
+               base = 0;
+               break;
+       default:
+               error = EINVAL;
+               goto out;
+       }
+
+       /* Check for arithmetic overflow and reject negative offsets.  */
+       if (base < 0 || delta > OFF_MAX - base || base + delta < 0) {
+               error = EINVAL;
+               goto out;
+       }
+
+       /* Compute the new offset.  */
+       newoff = base + delta;
+
+       /* Success!  */
+       if (newoffp)
+               *newoffp = newoff;
+       if (flags & FOF_UPDATE_OFFSET)
+               fp->f_offset = newoff;
+       error = 0;
+
+out:   mutex_exit(&fp->f_lock);
+       return error;
+}