On Fri, Aug 24, 2012 at 02:56:50PM +0530, Shirish S wrote:
The current logic for probing ddc is limited to 2 blocks (256 bytes), this patch adds support for the 4 block (512) data.
To do this, a single 8-bit segment index is passed to the display via the I2C address 30h. Data from the selected segment is then immediately read via the regular DDC2 address using a repeated I2C 'START' signal.
Signed-off-by: Shirish S s.shirish@samsung.com
drivers/gpu/drm/drm_edid.c | 83 ++++++++++++++++++++++++++++++++----------- 1 files changed, 62 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index a8743c3..a10a130 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -254,6 +254,8 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf, int block, int len) { unsigned char start = block * EDID_LENGTH;
- unsigned char segment = block >> 1;
- unsigned short segFlags = segment ? 0 : I2C_M_IGNORE_NAK;
You can inline segFlags to the only place it's used.
int ret, retries = 5;
/* The core i2c driver will automatically retry the transfer if the @@ -262,29 +264,68 @@ drm_do_probe_ddc_edid(struct i2c_adapter *adapter, unsigned char *buf, * generate spurious NAKs and timeouts. Retrying the transfer * of the individual block a few times seems to overcome this. */
- do {
struct i2c_msg msgs[] = {{.addr = DDC_ADDR,.flags = 0,.len = 1,.buf = &start,}, {.addr = DDC_ADDR,.flags = I2C_M_RD,.len = len,.buf = buf,
- switch (segment) {
/* To reduce traffic on I2C, we request the i2c xfer* for segment addr only if 4 block edid data is* present.* 0 : DDC* 1 : E-DDC*/
This comment is a bit misleading: We don't avoid the segment xfer to reduce i2c traffic, but to avoid upsetting any non-compliant screens.
- case 0:
do {
Keeping the loop as the outermost would imo be clearer and avoid duplicating it (it also would make the patch a bit smaller). You could even do a trick with the msgs array like this:
msgs[] = { full i2c xfer including segment addr} xfers = 3;
/* Avoid sending the segment addr to not upset non-compliant ddc * monitors. */ if (!segments) msgs++, len--;
i2c_transefer(adapter, msgs, len);
Also, I think it'd be good to set the IGNORE_NAK on the start addre transfer, too (but in a separate patch). At least I think we've seen screens out there that need this :(
Yours, Daniel
struct i2c_msg msgs[] = {{.addr = DDC_ADDR,.flags = 0,.len = 1,.buf = &start,}, {.addr = DDC_ADDR,.flags = I2C_M_RD,.len = len,.buf = buf,}};ret = i2c_transfer(adapter, msgs, 2);if (ret == -ENXIO) {DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",adapter->name);break; }
};ret = i2c_transfer(adapter, msgs, 2);if (ret == -ENXIO) {DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",adapter->name);break;}- } while (ret != 2 && --retries);
} while (ret != 2 && --retries);return ret == 2 ? 0 : -1;- case 1:
do {struct i2c_msg msgs[] = {{ /*set segment pointer */.addr = DDC_SEGMENT_ADDR,.flags = segFlags,.len = 1,.buf = &segment,}, { /*set offset */.addr = DDC_ADDR,.flags = 0,.len = 1,.buf = &start,}, { /*set data */.addr = DDC_ADDR,.flags = I2C_M_RD,.len = len,.buf = buf,}};ret = i2c_transfer(adapter, msgs, 3);if (ret == -ENXIO) {DRM_DEBUG_KMS("drm: skipping non-existent adapter %s\n",adapter->name);break;}} while (ret != 3 && --retries);
- return ret == 2 ? 0 : -1;
return ret == 3 ? 0 : -1;- }
- return -1;
}
static bool drm_edid_is_zero(u8 *in_edid, int length)
1.7.0.4
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