[PATCH v4 1/3] drm: Add user-defined EDID quirks capability

[Ian Pilcher <arequipeno@gmail.com>]

Add the ability for users to define their own EDID quirks via a
module parameter or sysfs attribute.

Signed-off-by: Ian Pilcher <arequipeno@gmail.com>
Acked-by: Paul Menzel <paulepanter@users.sourceforge.net>
---
 Documentation/EDID/edid_quirks.txt | 126 ++++++++++
 drivers/gpu/drm/drm_drv.c          |   2 +
 drivers/gpu/drm/drm_edid.c         | 500 ++++++++++++++++++++++++++++++++-----
 drivers/gpu/drm/drm_stub.c         |   6 +
 drivers/gpu/drm/drm_sysfs.c        |  19 ++
 include/drm/drmP.h                 |  10 +
 include/drm/drm_edid.h             |  13 +-
 7 files changed, 615 insertions(+), 61 deletions(-)
 create mode 100644 Documentation/EDID/edid_quirks.txt

diff --git a/Documentation/EDID/edid_quirks.txt b/Documentation/EDID/edid_quirks.txt
new file mode 100644
index 0000000..0c9c746
--- /dev/null
+++ b/Documentation/EDID/edid_quirks.txt
@@ -0,0 +1,126 @@
+                                  EDID Quirks
+                                 =============
+                       Ian Pilcher <arequipeno@gmail.com>
+                                August 11, 2012
+
+
+    "EDID blocks out in the wild have a variety of bugs"
+        -- from drivers/gpu/drm/drm_edid.c
+
+
+Overview
+========
+
+EDID quirks provide a mechanism for working around display hardware with buggy
+EDID data.
+
+An individual EDID quirk maps a display type (identified by its EDID
+manufacturer ID and product code[1]) to a set of "quirk flags."  The kernel
+includes a variety of built-in quirks.  (They are stored in the edid_quirk_list
+array in drivers/gpu/drm/drm_edid.c.)
+
+An example of a built-in EDID quirk is:
+
+    ACR:0xad46:0x00000001
+
+The first field is the manufacturer ID (Acer, Inc.), the second field is the
+manufacturer's product code, and the third field contains the quirk flags for
+that display type.
+
+The quirk flags are defined in drivers/gpu/drm/drm_edid.c.  Each flag has a
+symbolic name beginning with EDID_QUIRK_, along with a numerical value.  Each
+flag should also have an associated comment which provides an idea of its
+effect.  Note that the values in the source file are expressed as bit shifts[2]:
+
+    * 1 << 0: 0x0001
+    * 1 << 1: 0x0002
+    * 1 << 2: 0x0004
+    * etc.
+
+
+sysfs interface
+===============
+
+The current EDID quirk list can be read from /sys/class/drm/edid_quirks:
+
+    # cat /sys/class/drm/edid_quirks
+       ACR:0xad46:0x00000001
+       API:0x7602:0x00000001
+       ACR:0x0977:0x00000020
+    0x9e6a:0x077e:0x00000080
+    ...
+
+("Nonconformant" manufacturer IDs are displayed as hexadecimal values.)
+
+The number of total "slots" in the list can be read from
+/sys/class/drm/edid_quirks_size.  This total includes both occupied slots (i.e.
+the current list) and any slots available for additional quirks.  The number of
+available slots can be calculated by subtracting the number of quirks in the
+current list from the total number of slots.
+
+If a slot is available, an additional quirk can be added to the list by writing
+it to /sys/class/drm/edid_quirks:
+
+    # echo FOO:0xffff:0x100 > /sys/class/drm/edid_quirks
+
+Manufacturer IDs can also be specified numerically.  (This is the only way to
+specify a nonconformant ID.) This command is equivalent to the previous one:
+
+    # echo 0x19ef:0xffff:0x100 > /sys/class/drm/edid_quirks
+
+Numeric values can also be specified in decimal or octal formats; a number that
+begins with a 0 is assumed to be octal:
+
+    # echo FOO:65535:0400 > /sys/class/drm/edid_quirks
+
+An existing quirk can be replaced by writing a new set of flags:
+
+    # echo FOO:0xffff:0x200 > /sys/class/drm/edid_quirks
+
+A quirk can be deleted from the list by writing an empty flag set (0). This
+makes the slot occupied by that quirk available.
+
+    # echo FOO:0xffff:0 > /sys/class/drm/edid_quirks
+
+Writing an "at symbol" (@) clears the entire quirk list:
+
+    # echo @ > /sys/class/drm/edid_quirks
+
+Multiple changes to the list can be specified in a comma (or newline) separated
+list. For example, the following command clears all of the existing quirks in
+the list and adds 3 new quirks:
+
+    # echo @,FOO:0xffff:0x100,BAR:0x1111:0x001,BAZ:0x2222:0x002 > \
+            /sys/class/drm/edid_quirks
+
+Note however, that any error (an incorrectly formatted quirk or an attempt to
+add a quirk when no slot is available) will abort processing of any further
+changes, potentially making it difficult to determine exactly which change
+caused the error and what changes were made.  For this reason, making changes
+one at a time is recommended, particularly if the changes are being made by a
+script or program.
+
+
+Module parameter
+================
+
+The EDID quirk list can also be modified via the edid_quirks module parameter
+(drm.edid_quirks on the kernel command line).  The effect of setting this
+parameter is identical to the effect of writing its value to
+/sys/class/drm/edid_quirks, with one important difference.  When an error is
+encountered during module parameter parsing or processing, any remaining quirks
+in the parameter string will still be processed.  (It is hoped that this approach
+maximizes the probability of producing a working display.)
+
+
+Follow-up
+=========
+
+If you encounter a display that requires an additional EDID quirk in order to
+function properly, please report it to the direct rendering development mailing
+list <dri-devel@lists.freedesktop.org>.
+
+
+[1] See http://en.wikipedia.org/wiki/Extended_display_identification_data for a
+    description of the manufacturer ID and product code fields.
+[2] https://en.wikipedia.org/wiki/Bitwise_operation#Bit_shifts
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 9238de4..7fe39e0 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -276,6 +276,8 @@ static int __init drm_core_init(void)
 		goto err_p3;
 	}
 
+	drm_edid_quirks_param_process();
+
 	DRM_INFO("Initialized %s %d.%d.%d %s\n",
 		 CORE_NAME, CORE_MAJOR, CORE_MINOR, CORE_PATCHLEVEL, CORE_DATE);
 	return 0;
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index a8743c3..ea535f6 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -31,6 +31,8 @@
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
+#include <linux/ctype.h>
+
 #include "drmP.h"
 #include "drm_edid.h"
 #include "drm_edid_modes.h"
@@ -82,51 +84,457 @@ struct detailed_mode_closure {
 #define LEVEL_GTF2	2
 #define LEVEL_CVT	3
 
-static struct edid_quirk {
-	char vendor[4];
-	int product_id;
-	u32 quirks;
-} edid_quirk_list[] = {
+union edid_quirk {
+	struct {
+		union edid_display_id display_id;
+		u32 quirks;
+	} __attribute__((packed)) s;
+	u64 u;
+};
+
+#define EDID_MFG_ID(c1, c2, c3)		cpu_to_be16(			\
+						(c1 & 0x1f) << 10 |	\
+						(c2 & 0x1f) << 5 |	\
+						(c3 & 0x1f)		\
+					)
+
+#define EDID_QUIRK_LIST_SIZE	24
+
+union edid_quirk edid_quirk_list[EDID_QUIRK_LIST_SIZE] = {
+
 	/* Acer AL1706 */
-	{ "ACR", 44358, EDID_QUIRK_PREFER_LARGE_60 },
+	{ { { { EDID_MFG_ID('A', 'C', 'R'), cpu_to_le16(44358) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
 	/* Acer F51 */
-	{ "API", 0x7602, EDID_QUIRK_PREFER_LARGE_60 },
+	{ { { { EDID_MFG_ID('A', 'P', 'I'), cpu_to_le16(0x7602) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
 	/* Unknown Acer */
-	{ "ACR", 2423, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
+	{ { { { EDID_MFG_ID('A', 'C', 'R'), cpu_to_le16(2423) } },
+		EDID_QUIRK_FIRST_DETAILED_PREFERRED } },
 
 	/* Belinea 10 15 55 */
-	{ "MAX", 1516, EDID_QUIRK_PREFER_LARGE_60 },
-	{ "MAX", 0x77e, EDID_QUIRK_PREFER_LARGE_60 },
+	{ { { { EDID_MFG_ID('M', 'A', 'X'), cpu_to_le16(1516) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
+	{ { { { EDID_MFG_ID('M', 'A', 'X'), cpu_to_le16(0x77e) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
 
 	/* Envision Peripherals, Inc. EN-7100e */
-	{ "EPI", 59264, EDID_QUIRK_135_CLOCK_TOO_HIGH },
+	{ { { { EDID_MFG_ID('E', 'P', 'I'), cpu_to_le16(59264) } },
+		EDID_QUIRK_135_CLOCK_TOO_HIGH } },
 	/* Envision EN2028 */
-	{ "EPI", 8232, EDID_QUIRK_PREFER_LARGE_60 },
+	{ { { { EDID_MFG_ID('E', 'P', 'I'), cpu_to_le16(8232) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
 
 	/* Funai Electronics PM36B */
-	{ "FCM", 13600, EDID_QUIRK_PREFER_LARGE_75 |
-	  EDID_QUIRK_DETAILED_IN_CM },
+	{ { { { EDID_MFG_ID('F', 'C', 'M'), cpu_to_le16(13600) } },
+		EDID_QUIRK_PREFER_LARGE_75 | EDID_QUIRK_DETAILED_IN_CM } },
 
 	/* LG Philips LCD LP154W01-A5 */
-	{ "LPL", 0, EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE },
-	{ "LPL", 0x2a00, EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE },
+	{ { { { EDID_MFG_ID('L', 'P', 'L'), cpu_to_le16(0) } },
+		EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE } },
+	{ { { { EDID_MFG_ID('L', 'P', 'L'), cpu_to_le16(0x2a00) } },
+		EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE } },
 
 	/* Philips 107p5 CRT */
-	{ "PHL", 57364, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
+	{ { { { EDID_MFG_ID('P', 'H', 'L'), cpu_to_le16(57364) } },
+		EDID_QUIRK_FIRST_DETAILED_PREFERRED } },
 
 	/* Proview AY765C */
-	{ "PTS", 765, EDID_QUIRK_FIRST_DETAILED_PREFERRED },
+	{ { { { EDID_MFG_ID('P', 'T', 'S'), cpu_to_le16(765) } },
+		EDID_QUIRK_FIRST_DETAILED_PREFERRED } },
 
 	/* Samsung SyncMaster 205BW.  Note: irony */
-	{ "SAM", 541, EDID_QUIRK_DETAILED_SYNC_PP },
+	{ { { { EDID_MFG_ID('S', 'A', 'M'), cpu_to_le16(541) } },
+		EDID_QUIRK_DETAILED_SYNC_PP } },
 	/* Samsung SyncMaster 22[5-6]BW */
-	{ "SAM", 596, EDID_QUIRK_PREFER_LARGE_60 },
-	{ "SAM", 638, EDID_QUIRK_PREFER_LARGE_60 },
+	{ { { { EDID_MFG_ID('S', 'A', 'M'), cpu_to_le16(596) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
+	{ { { { EDID_MFG_ID('S', 'A', 'M'), cpu_to_le16(638) } },
+		EDID_QUIRK_PREFER_LARGE_60 } },
 
 	/* ViewSonic VA2026w */
-	{ "VSC", 5020, EDID_QUIRK_FORCE_REDUCED_BLANKING },
+	{ { { { EDID_MFG_ID('V', 'S', 'C'), cpu_to_le16(5020) } },
+		EDID_QUIRK_FORCE_REDUCED_BLANKING } },
+
+	/*
+	 * When adding built-in quirks, please adjust EDID_QUIRK_LIST_SIZE to
+	 * provide some room for user-supplied quirks.
+	 */
 };
 
+DEFINE_MUTEX(edid_quirk_list_mutex);
+
+/**
+ * drm_edid_mfg_format - format an "encoded" EDID manufacturer ID for printing
+ * @mfg_id: the encoded manufacturer ID
+ * @buf: destination buffer for the formatted manufacturer ID (minimum 7 bytes)
+ * @strip: if non-zero, the returned pointer will skip any leading spaces
+ *
+ * An EDID manufacturer ID is supposed to consist of 3 capital letters (A-Z).
+ * Each letter is stored as a 5-bit value between 1 and 26, taking up 15 bits of
+ * the 16-bit ID. The remaining bit should always be 0. If display manufacturers
+ * always did things correctly, however, EDID quirks wouldn't be required in
+ * the first place. This function does the following:
+ *
+ * - Broken IDs are printed in hexadecimal (0xffff).
+ * - "Correct" IDs are formatted as a 3-letter ID string, preceded by 3 spaces;
+ *   the spaces ensure that both output formats are the same length.
+ *
+ * Thus, a formatted manufacturer ID is always 6 characters long (not including
+ * the terminating 0).
+ *
+ * If @strip is 0, or the manufacturer ID has been formatted as a hexadecimal
+ * number, @buf is returned.  If @strip is non-zero, and the manufacturer ID has
+ * been formatted as a 3-letter string, a pointer to the first non-space
+ * character (@buf + 3) is returned.
+ */
+static const char *drm_edid_mfg_format(__be16 mfg_id, char *buf, int strip)
+{
+	u16 id = be16_to_cpu(mfg_id);
+
+	if (id & 0x8000)
+		goto bad_id;
+
+	buf[3] = ((id & 0x7c00) >> 10) + '@';
+	if (!isupper(buf[3]))
+		goto bad_id;
+
+	buf[4] = ((id & 0x03e0) >> 5) + '@';
+	if (!isupper(buf[4]))
+		goto bad_id;
+
+	buf[5] = (id & 0x001f) + '@';
+	if (!isupper(buf[5]))
+		goto bad_id;
+
+	memset(buf, ' ', 3);
+	buf[6] = 0;
+
+	return strip ? (buf + 3) : buf;
+
+bad_id:
+	sprintf(buf, "0x%04hx", id);
+	return buf;
+}
+
+#define EDID_MFG_BUF_SIZE		7
+
+/**
+ * drm_edid_display_id_format - format an EDID "display ID" (manufacturer ID
+ * 				and product code) for printing
+ * @display_id: the display ID
+ * @buf: destination buffer for the formatted display ID (minimum 14 bytes)
+ * @strip: if non-zero, the returned pointer will skip any leading spaces
+ *
+ * A formatted display ID is always 13 characters long (not including the
+ * terminating 0).
+ *
+ * If @strip is 0, or the manufacturer ID has been formatted as a hexadecimal
+ * number, @buf is returned.  If @strip is non-zero, and the manufacturer ID has
+ * been formatted as a 3-letter string, a pointer to the first non-space
+ * character (@buf + 3) is returned.
+ */
+static const char *drm_edid_display_id_format(union edid_display_id display_id,
+					      char *buf, int strip)
+{
+	const char *s;
+
+	s = drm_edid_mfg_format(display_id.s.mfg_id, buf, strip);
+	sprintf(buf + EDID_MFG_BUF_SIZE - 1, ":0x%04hx",
+		le16_to_cpu(display_id.s.prod_code));
+
+	return s;
+}
+
+#define EDID_DISPLAY_ID_BUF_SIZE	(EDID_MFG_BUF_SIZE + 7)
+
+/**
+ * drm_edid_quirk_format - format an EDID quirk for printing
+ * @quirk: the quirk
+ * @buf: destination buffer for the formatted quirk (minimum 25 bytes)
+ * @strip: if non-zero, the returned pointer will skip any leading spaces
+ *
+ * A formatted EDID quirk is always 24 characters long (not including the
+ * terminating 0).
+ *
+ * If @strip is 0, or the manufacturer ID has been formatted as a hexadecimal
+ * number, @buf is returned.  If @strip is non-zero, and the manufacturer ID has
+ * been formatted as a 3-letter string, a pointer to the first non-space
+ * character (@buf + 3) is returned.
+ */
+static const char *drm_edid_quirk_format(const union edid_quirk *quirk,
+					 char *buf, int strip)
+{
+	const char *s;
+
+	s = drm_edid_display_id_format(quirk->s.display_id, buf, strip);
+	sprintf(buf + EDID_DISPLAY_ID_BUF_SIZE - 1, ":0x%08x", quirk->s.quirks);
+
+	return s;
+}
+
+#define EDID_QUIRK_BUF_SIZE		(EDID_DISPLAY_ID_BUF_SIZE + 11)
+
+/**
+ * drm_edid_quirk_parse - parse an EDID quirk
+ * @s: string containing the quirk to be parsed
+ * @quirk: destination for parsed quirk
+ *
+ * Returns 0 on success, < 0 (currently -EINVAL) on error.
+ */
+static int drm_edid_quirk_parse(const char *s, union edid_quirk *quirk)
+{
+	char buf[EDID_QUIRK_BUF_SIZE];
+	s32 mfg;
+	s32 product;
+	s64 quirks;
+	char *c;
+
+	if (sscanf(s, "%i:%i:%lli", &mfg, &product, &quirks) == 3) {
+		if (mfg < 0 || mfg > 0xffff)
+			goto error;
+		quirk->s.display_id.s.mfg_id = cpu_to_be16((u16)mfg);
+	} else {
+		if (sscanf(s, "%3s:%i:%lli", buf, &product, &quirks) != 3 ||
+				!isupper(buf[0]) ||
+				!isupper(buf[1]) ||
+				!isupper(buf[2]))
+			goto error;
+		quirk->s.display_id.s.mfg_id =
+				EDID_MFG_ID(buf[0], buf[1], buf[2]);
+	}
+
+	if (product < 0 || product > 0xffff ||
+			quirks < 0 || quirks > 0xffffffffLL)
+		goto error;
+
+	quirk->s.display_id.s.prod_code = cpu_to_le16((u16)product);
+	quirk->s.quirks = (u32)quirks;
+
+	DRM_DEBUG("Successfully parsed EDID quirk: %s\n",
+		  drm_edid_quirk_format(quirk, buf, 1));
+
+	return 0;
+
+error:
+	c = strpbrk(s, ",\n");
+	if (c == NULL) {
+		printk(KERN_WARNING "Invalid EDID quirk: '%s'\n", s);
+	} else {
+		printk(KERN_WARNING "Invalid EDID quirk: '%.*s'\n",
+		      (int)(c - s), s);
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * drm_edid_quirk_find_by_id - find the EDID quirk matching a display ID
+ * @display_id: the display ID to match
+ *
+ * Caller MUST hold edid_quirk_list_mutex.
+ *
+ * Returns a pointer to the matching quirk list entry, NULL if no such entry
+ * exists.
+ */
+static union edid_quirk *drm_edid_quirk_find_by_id(union edid_display_id id)
+{
+	union edid_quirk *q = edid_quirk_list;
+
+	do {
+		if (q->s.display_id.u == id.u && q->s.quirks != 0)
+			return q;
+	} while (++q < edid_quirk_list + ARRAY_SIZE(edid_quirk_list));
+
+	return NULL;
+}
+
+/**
+ * drm_edid_quirk_find_slot - find an empty slot in the EDID quirk list
+ *
+ * Caller MUST hold edid_quirk_list_mutex.
+ *
+ * Returns a pointer to the first empty slot, NULL if no empty slots exist.
+ */
+static union edid_quirk *drm_edid_quirk_find_empty(void)
+{
+	union edid_quirk *q = edid_quirk_list;
+
+	do {
+		if (q->s.quirks == 0)
+			return q;
+	} while (++q < edid_quirk_list + ARRAY_SIZE(edid_quirk_list));
+
+	return NULL;
+}
+
+/**
+ * drm_edid_quirk_process - process a newly parsed EDID quirk
+ * @quirk: the quirk to be processed
+ *
+ * Depending on the newly parsed quirk and the contents of the quirks list, this
+ * function will add, remove, or replace a quirk.
+ *
+ * Returns 0 on success, < 0 on error (-ENOSPC if there is no free slot for a
+ * new quirk). Note that trying to remove a quirk that isn't present is not
+ * considered an error.
+ */
+static int drm_edid_quirk_process(const union edid_quirk *quirk)
+{
+	char buf[EDID_QUIRK_BUF_SIZE];
+	union edid_quirk *q;
+	int res = 0;
+
+	mutex_lock(&edid_quirk_list_mutex);
+
+	if (quirk->s.quirks == 0) {
+		DRM_INFO("Removing EDID quirk for display %s\n",
+			 drm_edid_display_id_format(quirk->s.display_id,
+						    buf, 1));
+		q = drm_edid_quirk_find_by_id(quirk->s.display_id);
+		if (q == NULL) {
+			printk(KERN_WARNING "No quirk found for display %s\n",
+			       drm_edid_display_id_format(quirk->s.display_id,
+							  buf, 1));
+		} else {
+			q->u = 0;
+		}
+	} else {
+		DRM_INFO("Adding EDID quirk: %s\n",
+			 drm_edid_quirk_format(quirk, buf, 1));
+		q = drm_edid_quirk_find_by_id(quirk->s.display_id);
+		if (q == NULL) {
+			q = drm_edid_quirk_find_empty();
+			if (q == NULL) {
+				printk(KERN_WARNING
+				       "No free slot in EDID quirk list\n");
+				res = -ENOSPC;
+			} else {
+				q->u = quirk->u;
+			}
+		} else {
+			DRM_INFO("Replacing existing quirk: %s\n",
+				 drm_edid_quirk_format(q, buf, 1));
+			q->s.quirks = quirk->s.quirks;
+		}
+	}
+
+	mutex_unlock(&edid_quirk_list_mutex);
+
+	return res;
+}
+
+/**
+ * drm_edid_quirks_process - parse and process a comma separated list of EDID
+ * 			     quirks
+ * @s: string containing the quirks to be processed
+ * @strict: if non-zero, any parsing or processing error aborts further
+ * 	    processing
+ *
+ * Returns 0 on success, < 0 if any error is encountered.  (If multiple errors
+ * occur when strict is set to 0, the last error encountered is returned.)
+ */
+static int drm_edid_quirks_process(const char *s, int strict)
+{
+	union edid_quirk quirk;
+	int res = 0;
+
+	do {
+
+		if (*s == '@') {
+			DRM_INFO("Clearing EDID quirk list\n");
+			mutex_lock(&edid_quirk_list_mutex);
+			memset(edid_quirk_list, 0, sizeof edid_quirk_list);
+			mutex_unlock(&edid_quirk_list_mutex);
+		} else {
+			res = drm_edid_quirk_parse(s, &quirk);
+			if (res != 0) {
+				if (strict)
+					goto error;
+				continue;
+			}
+
+			res = drm_edid_quirk_process(&quirk);
+			if (res != 0) {
+				if (strict)
+					goto error;
+			}
+		}
+
+		s = strpbrk(s, ",\n");
+
+	} while (s != NULL && *(++s) != 0);
+
+	return res;
+
+error:
+	printk(KERN_WARNING "Aborting EDID quirk parsing\n");
+	return res;
+}
+
+/**
+ * drm_edid_quirks_param_process - process the edid_quirks module parameter
+ */
+void drm_edid_quirks_param_process(void)
+{
+	if (drm_edid_quirks != NULL)
+		drm_edid_quirks_process(drm_edid_quirks, 0);
+}
+
+/**
+ * drm_edid_quirks_size_show - show the size of the EDID quirk list in sysfs
+ * @buf: destination buffer (PAGE_SIZE bytes)
+ */
+ssize_t drm_edid_quirks_size_show(struct class *class,
+				  struct class_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%zu\n", ARRAY_SIZE(edid_quirk_list));
+}
+
+/**
+ * drm_edid_quirks_show - show the contents of the EDID quirk list in sysfs
+ * @buf: destination buffer (PAGE_SIZE bytes)
+ */
+ssize_t drm_edid_quirks_show(struct class *class, struct class_attribute *attr,
+			     char *buf)
+{
+	const union edid_quirk *q = edid_quirk_list;
+	ssize_t count = 0;
+
+	BUILD_BUG_ON(ARRAY_SIZE(edid_quirk_list) >
+				PAGE_SIZE / EDID_QUIRK_BUF_SIZE);
+
+	mutex_lock(&edid_quirk_list_mutex);
+
+	do {
+		if (q->s.quirks != 0) {
+			drm_edid_quirk_format(q, buf + count, 0);
+			(buf + count)[EDID_QUIRK_BUF_SIZE - 1] = '\n';
+			count += EDID_QUIRK_BUF_SIZE;
+		}
+	} while (++q < edid_quirk_list + ARRAY_SIZE(edid_quirk_list));
+
+	mutex_unlock(&edid_quirk_list_mutex);
+
+	return count;
+}
+
+/**
+ * drm_edid_quirks_store - parse and process EDID qurik list changes written
+ *			   to sysfs attribute
+ */
+ssize_t drm_edid_quirks_store(struct class *class, struct class_attribute *attr,
+			      const char *buf, size_t count)
+{
+	int res;
+
+	res = drm_edid_quirks_process(buf, 1);
+	if (res != 0)
+		return res;
+
+	return count;
+}
+
 /*** DDC fetch and block validation ***/
 
 static const u8 edid_header[] = {
@@ -409,25 +817,6 @@ EXPORT_SYMBOL(drm_get_edid);
 /*** EDID parsing ***/
 
 /**
- * edid_vendor - match a string against EDID's obfuscated vendor field
- * @edid: EDID to match
- * @vendor: vendor string
- *
- * Returns true if @vendor is in @edid, false otherwise
- */
-static bool edid_vendor(struct edid *edid, char *vendor)
-{
-	char edid_vendor[3];
-
-	edid_vendor[0] = ((edid->mfg_id[0] & 0x7c) >> 2) + '@';
-	edid_vendor[1] = (((edid->mfg_id[0] & 0x3) << 3) |
-			  ((edid->mfg_id[1] & 0xe0) >> 5)) + '@';
-	edid_vendor[2] = (edid->mfg_id[1] & 0x1f) + '@';
-
-	return !strncmp(edid_vendor, vendor, 3);
-}
-
-/**
  * edid_get_quirks - return quirk flags for a given EDID
  * @edid: EDID to process
  *
@@ -435,18 +824,18 @@ static bool edid_vendor(struct edid *edid, char *vendor)
  */
 static u32 edid_get_quirks(struct edid *edid)
 {
-	struct edid_quirk *quirk;
-	int i;
+	union edid_quirk *q;
+	u32 quirks = 0;
 
-	for (i = 0; i < ARRAY_SIZE(edid_quirk_list); i++) {
-		quirk = &edid_quirk_list[i];
+	mutex_lock(&edid_quirk_list_mutex);
 
-		if (edid_vendor(edid, quirk->vendor) &&
-		    (EDID_PRODUCT_ID(edid) == quirk->product_id))
-			return quirk->quirks;
-	}
+	q = drm_edid_quirk_find_by_id(edid->display_id);
+	if (q != NULL)
+		quirks = q->s.quirks;
 
-	return 0;
+	mutex_unlock(&edid_quirk_list_mutex);
+
+	return quirks;
 }
 
 #define MODE_SIZE(m) ((m)->hdisplay * (m)->vdisplay)
@@ -1162,7 +1551,7 @@ do_inferred_modes(struct detailed_timing *timing, void *c)
 	closure->modes += drm_dmt_modes_for_range(closure->connector,
 						  closure->edid,
 						  timing);
-	
+
 	if (!version_greater(closure->edid, 1, 1))
 		return; /* GTF not defined yet */
 
@@ -1399,7 +1788,7 @@ do_cvt_mode(struct detailed_timing *timing, void *c)
 
 static int
 add_cvt_modes(struct drm_connector *connector, struct edid *edid)
-{	
+{
 	struct detailed_mode_closure closure = {
 		connector, edid, 0, 0, 0
 	};
@@ -1615,15 +2004,12 @@ void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
 
 	eld[0] = 2 << 3;		/* ELD version: 2 */
 
-	eld[16] = edid->mfg_id[0];
-	eld[17] = edid->mfg_id[1];
-	eld[18] = edid->prod_code[0];
-	eld[19] = edid->prod_code[1];
+	*(u32 *)(&eld[16]) = edid->display_id.u;
 
 	if (cea[1] >= 3)
 		for (db = cea + 4; db < cea + cea[2]; db += dbl + 1) {
 			dbl = db[0] & 0x1f;
-			
+
 			switch ((db[0] & 0xe0) >> 5) {
 			case AUDIO_BLOCK:
 				/* Audio Data Block, contains SADs */
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 21bcd4a..b939d51 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -46,16 +46,22 @@ EXPORT_SYMBOL(drm_vblank_offdelay);
 unsigned int drm_timestamp_precision = 20;  /* Default to 20 usecs. */
 EXPORT_SYMBOL(drm_timestamp_precision);
 
+char *drm_edid_quirks = NULL;
+EXPORT_SYMBOL(drm_edid_quirks);
+
 MODULE_AUTHOR(CORE_AUTHOR);
 MODULE_DESCRIPTION(CORE_DESC);
 MODULE_LICENSE("GPL and additional rights");
 MODULE_PARM_DESC(debug, "Enable debug output");
 MODULE_PARM_DESC(vblankoffdelay, "Delay until vblank irq auto-disable [msecs]");
 MODULE_PARM_DESC(timestamp_precision_usec, "Max. error on timestamps [usecs]");
+MODULE_PARM_DESC(edid_quirks, "MFG:prod:flags[,MFG:prod:flags[...]]\n"
+			      "(See Documentation/EDID/edid_quirks.txt)");
 
 module_param_named(debug, drm_debug, int, 0600);
 module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600);
 module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);
+module_param_named(edid_quirks, drm_edid_quirks, charp, 0400);
 
 struct idr drm_minors_idr;
 
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 45ac8d6..84dc365 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -84,6 +84,11 @@ static CLASS_ATTR_STRING(version, S_IRUGO,
 		__stringify(CORE_PATCHLEVEL) " "
 		CORE_DATE);
 
+static CLASS_ATTR(edid_quirks_size, 0400, drm_edid_quirks_size_show, 0);
+
+static CLASS_ATTR(edid_quirks, 0600, drm_edid_quirks_show,
+		  drm_edid_quirks_store);
+
 /**
  * drm_sysfs_create - create a struct drm_sysfs_class structure
  * @owner: pointer to the module that is to "own" this struct drm_sysfs_class
@@ -113,10 +118,22 @@ struct class *drm_sysfs_create(struct module *owner, char *name)
 	if (err)
 		goto err_out_class;
 
+	err = class_create_file(class, &class_attr_edid_quirks_size);
+	if (err)
+		goto err_out_version;
+
+	err = class_create_file(class, &class_attr_edid_quirks);
+	if (err)
+		goto err_out_quirks_size;
+
 	class->devnode = drm_devnode;
 
 	return class;
 
+err_out_quirks_size:
+	class_remove_file(class, &class_attr_edid_quirks_size);
+err_out_version:
+	class_remove_file(class, &class_attr_version.attr);
 err_out_class:
 	class_destroy(class);
 err_out:
@@ -132,6 +149,8 @@ void drm_sysfs_destroy(void)
 {
 	if ((drm_class == NULL) || (IS_ERR(drm_class)))
 		return;
+	class_remove_file(drm_class, &class_attr_edid_quirks);
+	class_remove_file(drm_class, &class_attr_edid_quirks_size);
 	class_remove_file(drm_class, &class_attr_version.attr);
 	class_destroy(drm_class);
 	drm_class = NULL;
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index d6b67bb..c947f3e 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1501,6 +1501,7 @@ extern unsigned int drm_debug;
 
 extern unsigned int drm_vblank_offdelay;
 extern unsigned int drm_timestamp_precision;
+extern char *drm_edid_quirks;
 
 extern struct class *drm_class;
 extern struct proc_dir_entry *drm_proc_root;
@@ -1612,6 +1613,15 @@ void drm_gem_vm_open(struct vm_area_struct *vma);
 void drm_gem_vm_close(struct vm_area_struct *vma);
 int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
 
+					/* EDID support (drm_edid.c) */
+void drm_edid_quirks_param_process(void);
+ssize_t drm_edid_quirks_size_show(struct class *class,
+				  struct class_attribute *attr, char *buf);
+ssize_t drm_edid_quirks_show(struct class *class, struct class_attribute *attr,
+			     char *buf);
+ssize_t drm_edid_quirks_store(struct class *class, struct class_attribute *attr,
+			      const char *buf, size_t count);
+
 #include "drm_global.h"
 
 static inline void
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 0cac551..713229b 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -202,11 +202,18 @@ struct detailed_timing {
 #define DRM_EDID_FEATURE_PM_SUSPEND       (1 << 6)
 #define DRM_EDID_FEATURE_PM_STANDBY       (1 << 7)
 
+union edid_display_id {
+	struct {
+		__be16 mfg_id;
+		__le16 prod_code;
+	} __attribute__((packed)) s;
+	u32 u;
+};
+
 struct edid {
 	u8 header[8];
 	/* Vendor & product info */
-	u8 mfg_id[2];
-	u8 prod_code[2];
+	union edid_display_id display_id;
 	u32 serial; /* FIXME: byte order */
 	u8 mfg_week;
 	u8 mfg_year;
@@ -242,8 +249,6 @@ struct edid {
 	u8 checksum;
 } __attribute__((packed));
 
-#define EDID_PRODUCT_ID(e) ((e)->prod_code[0] | ((e)->prod_code[1] << 8))
-
 struct drm_encoder;
 struct drm_connector;
 struct drm_display_mode;
-- 
1.7.11.2