drm/udl: Reading all edid blocks in DRM/UDL driver

Now DRM/UDL driver retreives all edid data blocks instead of only base one.
Previous approch could lead to improper initialization of video mode with
certain monitors.

Signed-off-by: Robert Tarasov <tutankhamen@chromium.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013001350.172155-2-tutankhamen@chromium.org

1 files changed, 68 insertions, 38 deletions

diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c
index b4d1464d2d87..c0bbd1ce15f0 100644
--- a/drivers/gpu/drm/udl/udl_connector.c
+++ b/drivers/gpu/drm/udl/udl_connector.c
@@ -17,42 +17,79 @@
 #include "udl_connector.h"
 #include "udl_drv.h"
 
-/* dummy connector to just get EDID,
-   all UDL appear to have a DVI-D */
-
-static u8 *udl_get_edid(struct udl_device *udl)
+static bool udl_get_edid_block(struct udl_device *udl, int block_idx,
+                                                           u8 *buff)
 {
-        u8 *block;
-        char *rbuf;
         int ret, i;
+        u8 *read_buff;
 
-        block = kmalloc(EDID_LENGTH, GFP_KERNEL);
-        if (block == NULL)
-                return NULL;
-
-        rbuf = kmalloc(2, GFP_KERNEL);
-        if (rbuf == NULL)
-                goto error;
+        read_buff = kmalloc(2, GFP_KERNEL);
+        if (!read_buff)
+                return false;
 
         for (i = 0; i < EDID_LENGTH; i++) {
+                int bval = (i + block_idx * EDID_LENGTH) << 8;
                 ret = usb_control_msg(udl->udev,
-                                      usb_rcvctrlpipe(udl->udev, 0), (0x02),
-                                      (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
-                                      HZ);
+                                      usb_rcvctrlpipe(udl->udev, 0),
+                                          (0x02), (0x80 | (0x02 << 5)), bval,
+                                          0xA1, read_buff, 2, HZ);
                 if (ret < 1) {
                         DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret);
-                        goto error;
+                        kfree(read_buff);
+                        return false;
                 }
-                block[i] = rbuf[1];
+                buff[i] = read_buff[1];
         }
 
-        kfree(rbuf);
-        return block;
+        kfree(read_buff);
+        return true;
+}
 
-error:
-        kfree(block);
-        kfree(rbuf);
-        return NULL;
+static bool udl_get_edid(struct udl_device *udl, u8 **result_buff,
+                         int *result_buff_size)
+{
+        int i, extensions;
+        u8 *block_buff = NULL, *buff_ptr;
+
+        block_buff = kmalloc(EDID_LENGTH, GFP_KERNEL);
+        if (block_buff == NULL)
+                return false;
+
+        if (udl_get_edid_block(udl, 0, block_buff) &&
+            memchr_inv(block_buff, 0, EDID_LENGTH)) {
+                extensions = ((struct edid *)block_buff)->extensions;
+                if (extensions > 0) {
+                        /* we have to read all extensions one by one */
+                        *result_buff_size = EDID_LENGTH * (extensions + 1);
+                        *result_buff = kmalloc(*result_buff_size, GFP_KERNEL);
+                        buff_ptr = *result_buff;
+                        if (buff_ptr == NULL) {
+                                kfree(block_buff);
+                                return false;
+                        }
+                        memcpy(buff_ptr, block_buff, EDID_LENGTH);
+                        kfree(block_buff);
+                        buff_ptr += EDID_LENGTH;
+                        for (i = 1; i < extensions; ++i) {
+                                if (udl_get_edid_block(udl, i, buff_ptr)) {
+                                        buff_ptr += EDID_LENGTH;
+                                } else {
+                                        kfree(*result_buff);
+                                        *result_buff = NULL;
+                                        return false;
+                                }
+                        }
+                        return true;
+                }
+                /* we have only base edid block */
+                *result_buff = block_buff;
+                *result_buff_size = EDID_LENGTH;
+                return true;
+        }
+
+        kfree(block_buff);
+
+        return false;
 }
 
 static int udl_get_modes(struct drm_connector *connector)
@@ -84,33 +121,26 @@ static int udl_mode_valid(struct drm_connector *connector,
 static enum drm_connector_status
 udl_detect(struct drm_connector *connector, bool force)
 {
-        struct edid *edid;
+        u8 *edid_buff = NULL;
+        int edid_buff_size = 0;
         struct udl_device *udl = connector->dev->dev_private;
         struct udl_drm_connector *udl_connector =
                                         container_of(connector,
                                         struct udl_drm_connector,
                                         connector);
 
+        /* cleanup previous edid */
         if (udl_connector->edid != NULL) {
                 kfree(udl_connector->edid);
                 udl_connector->edid = NULL;
         }
 
-        edid = (struct edid *)udl_get_edid(udl);
-        if (!edid || !memchr_inv(edid, 0, EDID_LENGTH))
-                return connector_status_disconnected;
 
-        udl_connector->edid = edid;
-
-        /*
-         * We only read the main block, but if the monitor reports extension
-         * blocks then the drm edid code expects them to be present, so patch
-         * the extension count to 0.
-         */
-        udl_connector->edid->checksum +=
-                        udl_connector->edid->extensions;
-        udl_connector->edid->extensions = 0;
+        if (!udl_get_edid(udl, &edid_buff, &edid_buff_size))
+                return connector_status_disconnected;
 
+        udl_connector->edid = (struct edid *)edid_buff;
+        
         return connector_status_connected;
 }