Add a new so_seek member to "struct file" such that we can have seekable

files that aren't vnodes.  Move the vnode-specific code into its own
function.  Add an implementation for the "DMA buffers" that can be used
by DRI3/prime code to find out the size of the graphics buffer.
This implementation is very limited and only supports offset 0 and only
for SEEK_SET and SEEK_END.  This doesn't really make sense; implementing
stat(2) would be a more obvious choice.  But this is what Linux does.

ok guenther@, visa@

4 files changed, 83 insertions, 42 deletions

diff --git a/sys/dev/pci/drm/drm_linux.c b/sys/dev/pci/drm/drm_linux.c
index 4205b46291a..6564fd89b2a 100644
--- a/sys/dev/pci/drm/drm_linux.c
+++ b/sys/dev/pci/drm/drm_linux.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: drm_linux.c,v 1.25 2018/07/01 12:12:14 kettenis Exp $	*/
+/*	$OpenBSD: drm_linux.c,v 1.26 2018/07/03 20:40:25 kettenis Exp $	*/
 /*
  * Copyright (c) 2013 Jonathan Gray <jsg@openbsd.org>
  * Copyright (c) 2015, 2016 Mark Kettenis <kettenis@openbsd.org>
@@ -22,6 +22,7 @@
 #include <sys/file.h>
 #include <sys/filedesc.h>
 #include <sys/stat.h>
+#include <sys/unistd.h>
 
 struct mutex sch_mtx = MUTEX_INITIALIZER(IPL_SCHED);
 void *sch_ident;
@@ -859,6 +860,29 @@ dmabuf_close(struct file *fp, struct proc *p)
 	return (0);
 }
 
+int
+dmabuf_seek(struct file *fp, off_t *offset, int whence, struct proc *p)
+{
+	struct dma_buf *dmabuf = fp->f_data;
+	off_t newoff;
+
+	if (*offset != 0)
+		return (EINVAL);
+
+	switch (whence) {
+	case SEEK_SET:
+		newoff = 0;
+		break;
+	case SEEK_END:
+		newoff = dmabuf->size;
+		break;
+	default:
+		return (EINVAL);
+	}
+	fp->f_offset = *offset = newoff;
+	return (0);
+}
+
 struct fileops dmabufops = {
 	.fo_read	= dmabuf_read,
 	.fo_write	= dmabuf_write,
@@ -866,7 +890,8 @@ struct fileops dmabufops = {
 	.fo_poll	= dmabuf_poll,
 	.fo_kqfilter	= dmabuf_kqfilter,
 	.fo_stat	= dmabuf_stat,
-	.fo_close	= dmabuf_close
+	.fo_close	= dmabuf_close,
+	.fo_seek	= dmabuf_seek,
 };
 
 struct dma_buf *
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index ffc171b6576..da74978c8da 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_syscalls.c,v 1.291 2018/06/25 16:06:27 visa Exp $	*/
+/*	$OpenBSD: vfs_syscalls.c,v 1.292 2018/07/03 20:40:25 kettenis Exp $	*/
 /*	$NetBSD: vfs_syscalls.c,v 1.71 1996/04/23 10:29:02 mycroft Exp $	*/
 
 /*
@@ -1621,51 +1621,24 @@ sys_lseek(struct proc *p, void *v, register_t *retval)
 		syscallarg(off_t) offset;
 		syscallarg(int) whence;
 	} */ *uap = v;
-	struct ucred *cred = p->p_ucred;
 	struct filedesc *fdp = p->p_fd;
 	struct file *fp;
-	struct vattr vattr;
-	struct vnode *vp;
-	off_t offarg, newoff;
-	int error, special;
+	off_t offset;
+	int error;
 
 	if ((fp = fd_getfile(fdp, SCARG(uap, fd))) == NULL)
 		return (EBADF);
-	vp = fp->f_data;
-	if (fp->f_type != DTYPE_VNODE || vp->v_type == VFIFO) {
+	if (fp->f_ops->fo_seek == NULL) {
 		error = ESPIPE;
 		goto bad;
 	}
-	if (vp->v_type == VCHR)
-		special = 1;
-	else
-		special = 0;
-	offarg = SCARG(uap, offset);
-
-	switch (SCARG(uap, whence)) {
-	case SEEK_CUR:
-		newoff = fp->f_offset + offarg;
-		break;
-	case SEEK_END:
-		error = VOP_GETATTR(vp, &vattr, cred, p);
-		if (error)
-			goto bad;
-		newoff = offarg + (off_t)vattr.va_size;
-		break;
-	case SEEK_SET:
-		newoff = offarg;
-		break;
-	default:
-		error = EINVAL;
+	offset = SCARG(uap, offset);
+
+	error = (*fp->f_ops->fo_seek)(fp, &offset, SCARG(uap, whence), p);
+	if (error)
 		goto bad;
-	}
-	if (!special) {
-		if (newoff < 0) {
-			error = EINVAL;
-			goto bad;
-		}
-	}
-	*(off_t *)retval = fp->f_offset = newoff;
+
+	*(off_t *)retval = offset;
 	mtx_enter(&fp->f_mtx);
 	fp->f_seek++;
 	mtx_leave(&fp->f_mtx);
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 2dbc93adba4..c20982e0308 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vfs_vnops.c,v 1.94 2018/07/03 12:58:18 anton Exp $	*/
+/*	$OpenBSD: vfs_vnops.c,v 1.95 2018/07/03 20:40:25 kettenis Exp $	*/
 /*	$NetBSD: vfs_vnops.c,v 1.20 1996/02/04 02:18:41 christos Exp $	*/
 
 /*
@@ -64,6 +64,7 @@ int vn_write(struct file *, off_t *, struct uio *, struct ucred *);
 int vn_poll(struct file *, int, struct proc *);
 int vn_kqfilter(struct file *, struct knote *);
 int vn_closefile(struct file *, struct proc *);
+int vn_seek(struct file *, off_t *, int, struct proc *);
 
 struct 	fileops vnops = {
 	.fo_read	= vn_read,
@@ -72,7 +73,8 @@ struct 	fileops vnops = {
 	.fo_poll	= vn_poll,
 	.fo_kqfilter	= vn_kqfilter,
 	.fo_stat	= vn_statfile,
-	.fo_close	= vn_closefile
+	.fo_close	= vn_closefile,
+	.fo_seek	= vn_seek,
 };
 
 /*
@@ -561,6 +563,46 @@ vn_kqfilter(struct file *fp, struct knote *kn)
 	return (VOP_KQFILTER(fp->f_data, kn));
 }
 
+int
+vn_seek(struct file *fp, off_t *offset, int whence, struct proc *p)
+{
+	struct ucred *cred = p->p_ucred;
+	struct vnode *vp = fp->f_data;
+	struct vattr vattr;
+	off_t newoff;
+	int error, special;
+
+	if (vp->v_type == VFIFO)
+		return (ESPIPE);
+	if (vp->v_type == VCHR)
+		special = 1;
+	else
+		special = 0;
+
+	switch (whence) {
+	case SEEK_CUR:
+		newoff = fp->f_offset + *offset;
+		break;
+	case SEEK_END:
+		error = VOP_GETATTR(vp, &vattr, cred, p);
+		if (error)
+			return (error);
+		newoff = *offset + (off_t)vattr.va_size;
+		break;
+	case SEEK_SET:
+		newoff = *offset;
+		break;
+	default:
+		return (EINVAL);
+	}
+	if (!special) {
+		if (newoff < 0)
+			return(EINVAL);
+	}
+	fp->f_offset = *offset = newoff;
+	return (0);
+}
+
 /*
  * Common code for vnode access operations.
  */
diff --git a/sys/sys/file.h b/sys/sys/file.h
index 114c192d766..ef543367479 100644
--- a/sys/sys/file.h
+++ b/sys/sys/file.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: file.h,v 1.51 2018/07/02 14:36:33 visa Exp $	*/
+/*	$OpenBSD: file.h,v 1.52 2018/07/03 20:40:25 kettenis Exp $	*/
 /*	$NetBSD: file.h,v 1.11 1995/03/26 20:24:13 jtc Exp $	*/
 
 /*
@@ -57,6 +57,7 @@ struct	fileops {
 	int	(*fo_kqfilter)(struct file *, struct knote *);
 	int	(*fo_stat)(struct file *, struct stat *, struct proc *);
 	int	(*fo_close)(struct file *, struct proc *);
+	int	(*fo_seek)(struct file *, off_t *, int, struct proc *);
 };
 
 /*