dri-devel Archive on lore.kernel.org
 help / color / Atom feed
From: Mauro Rossi <issor.oruam@gmail.com>
To: dri-devel@lists.freedesktop.org
Cc: robert.foss@collabora.com, Mauro Rossi <issor.oruam@gmail.com>,
	emil.l.velikov@gmail.com, cwhuang@linux.org.tw
Subject: [PATCH] xf86drm: add drmOpenByFB
Date: Sat, 23 May 2020 17:44:26 +0200
Message-ID: <20200523154426.1088988-1-issor.oruam@gmail.com> (raw)

OpenByFB is introduced to overcome GPU driver loading order issue
on a device with multiple GPUs, e.g. Intel iGPU and Nvidia dGPU
where the first drmfb kernel module loaded will become device file
/dev/dri/card0 and the second will become /dev/dri/card1

The use case is to prefer Intel iGPU over dGPU, or viceversa,
in a deterministic and reliable manner.

OpenByFB function opens the DRM device with specified fb and node type,
thus enabling gralloc to open the correct device node of the primary fb,
regardless of the GPU driver loading order.

Signed-off-by: Chih-Wei Huang <cwhuang@linux.org.tw>
---
 core-symbols.txt |  1 +
 xf86drm.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 xf86drm.h        |  1 +
 3 files changed, 44 insertions(+)

diff --git a/core-symbols.txt b/core-symbols.txt
index 1ff4ecaa..6bf8c70d 100644
--- a/core-symbols.txt
+++ b/core-symbols.txt
@@ -146,6 +146,7 @@ drmModeSetCursor2
 drmModeSetPlane
 drmMsg
 drmOpen
+drmOpenByFB
 drmOpenControl
 drmOpenOnce
 drmOpenOnceWithType
diff --git a/xf86drm.c b/xf86drm.c
index b49d42f7..229a54bf 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -793,6 +793,48 @@ drm_public int drmOpenRender(int minor)
     return drmOpenMinor(minor, 0, DRM_NODE_RENDER);
 }
 
+/**
+ * Open the DRM device with specified type of specified framebuffer.
+ *
+ * Looks up the associated DRM device with specified type of the
+ * specified framebuffer and opens it.
+ *
+ * \param fb the index of framebuffer.
+ * \param type the device node type to open, PRIMARY, CONTROL or RENDER
+ *
+ * \return a file descriptor on success, or a negative value on error.
+ *
+ */
+drm_public int drmOpenByFB(int fb, int type)
+{
+#ifdef __linux__
+    DIR *sysdir;
+    struct dirent *ent;
+    char buf[64];
+    const char *name = drmGetMinorName(type);
+    int fd = -1, len = strlen(name);
+
+    snprintf(buf, sizeof(buf), "/sys/class/graphics/fb%d/device/drm", fb);
+    sysdir = opendir(buf);
+    if (!sysdir)
+        return -errno;
+
+    while ((ent = readdir(sysdir))) {
+        if (!strncmp(ent->d_name, name, len)) {
+            snprintf(buf, sizeof(buf), "%s/%s", DRM_DIR_NAME, ent->d_name);
+            fd = open(buf, O_RDWR | O_CLOEXEC, 0);
+            break;
+        }
+    }
+
+    closedir(sysdir);
+    return fd;
+#else
+#warning "Missing implementation of drmOpenByFB"
+    return -EINVAL;
+#endif
+}
+
 /**
  * Free the version information returned by drmGetVersion().
  *
diff --git a/xf86drm.h b/xf86drm.h
index 7b85079a..d45d696f 100644
--- a/xf86drm.h
+++ b/xf86drm.h
@@ -605,6 +605,7 @@ extern int           drmOpenWithType(const char *name, const char *busid,
 
 extern int           drmOpenControl(int minor);
 extern int           drmOpenRender(int minor);
+extern int           drmOpenByFB(int fb, int type);
 extern int           drmClose(int fd);
 extern drmVersionPtr drmGetVersion(int fd);
 extern drmVersionPtr drmGetLibVersion(int fd);
-- 
2.25.1

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

             reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-23 15:44 Mauro Rossi [this message]
2020-05-23 21:36 ` Simon Ser
2020-05-24 18:53 ` Daniel Vetter
2020-05-24 19:25   ` Simon Ser
2020-05-28  9:46     ` Chih-Wei Huang
2020-05-28 12:38       ` Emil Velikov
2020-05-29  7:48       ` Pekka Paalanen
2020-05-29 14:20         ` Alex Deucher

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200523154426.1088988-1-issor.oruam@gmail.com \
    --to=issor.oruam@gmail.com \
    --cc=cwhuang@linux.org.tw \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=emil.l.velikov@gmail.com \
    --cc=robert.foss@collabora.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

dri-devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/dri-devel/0 dri-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dri-devel dri-devel/ https://lore.kernel.org/dri-devel \
		dri-devel@lists.freedesktop.org
	public-inbox-index dri-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.freedesktop.lists.dri-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git