[PATCH v4 1/2] media: atomisp: csi2: Remove unimplemented DPCM decompression

[Debjeet Banerjee <debjeetbanerjee48@gmail.com>]

The source pad format handling attempted to map DPCM-compressed mbus
codes to their uncompressed equivalents. However, the rest of the
driver does not support DPCM decompression, making this dead code.

Remove the DPCM unmapping logic and simplify to directly copy the sink
pad format to the source pad. Add an explicit comment stating that
DPCM is not supported.

Signed-off-by: Debjeet Banerjee <debjeetbanerjee48@gmail.com>
---
v4:
- Complete removal of DPCM decompression attempt (per Sakari Ailus feedback)
- Keep source pad simply copying sink pad format without unmapping
- Replace detailed comment with explicit "DPCM is not supported" statement

v3:
- Drop "staging:" prefix in subject (per Andy Shevchenko)

v2:
- Rebased onto latest media tree (fix CI apply failure)
- Fix missing linux-staging recipient (typo in v1)
- Fix indentation
---
 drivers/staging/media/atomisp/pci/atomisp_csi2.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/media/atomisp/pci/atomisp_csi2.c b/drivers/staging/media/atomisp/pci/atomisp_csi2.c
index e723304bec80..64419c1a805e 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_csi2.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_csi2.c
@@ -107,17 +107,10 @@ int atomisp_csi2_set_ffmt(struct v4l2_subdev *sd,
 					     &tmp_ffmt);
 	}
 
-	/*
-	 * The source pad must expose the uncompressed format even when the sink
-	 * pad receives DPCM-compressed data. The hardware decompresses DPCM
-	 * (e.g. SGRBG10_DPCM8_1X8 -> SGRBG10_1X10) between sink and source,
-	 * so propagate the sink format but map the mbus code to its uncompressed
-	 * equivalent. atomisp_subdev_uncompressed_code() returns the code
-	 * unchanged for formats that are not DPCM-compressed.
-	 */
-	*actual_ffmt = *__csi2_get_format(csi2, sd_state, which, CSI2_PAD_SINK);
-	actual_ffmt->code = atomisp_subdev_uncompressed_code(actual_ffmt->code);
-	*ffmt = *actual_ffmt;
+	/* Source pad format is copied from sink pad. DPCM is not supported. */
+	*actual_ffmt = *ffmt = *__csi2_get_format(csi2, sd_state, which,
+						  CSI2_PAD_SINK);
+
 	return 0;
 }
 
-- 
2.53.0