Re: [PATCH] staging: fbtft: fix unaligned access and txbuf safety issues

On Thu, Jun 25, 2026 at 07:42:15PM +0800, suryasaimadhu wrote:

This patch addresses several pre-existing issues in the fbtft driver:

1. define_fbtft_write_reg(): when par->startbyte is set, buf is
   advanced by one byte creating a misaligned pointer for 16-bit types.
   Use put_unaligned() for register writes and fix the SPI transfer
   size from len * (sizeof(data_type) + offset) to
   len * sizeof(data_type) + offset.

2. fbtft_write_vmem16_bus8() and fb_ra8875 write_vmem16_bus8(): same
   unaligned 16-bit stores when txbuf is byte-offset for a start
   prefix. Use put_unaligned() for pixel data copies.

3. tx_array_size underflow: both vmem helpers subtract 2 from
   tx_array_size when a startbyte prefix is used. A small txbuflen
   device property causes unsigned underflow and out-of-bounds heap
   writes. Fall back to the non-buffered write path when the buffer
   is too small.

4. fb_ra8875 write_vmem16_bus8(): missing NULL check for
   par->txbuf.buf, which remains NULL on big-endian when txbuflen is
   0 because the PAGE_SIZE fallback is little-endian only. Fall back
   to direct write when the buffer is missing.

Also replace empty modifier arguments in define_fbtft_write_reg() with
a no-op macro to fix checkpatch warnings.

Signed-off-by: suryasaimadhu <redacted>

Is this how you would sign a legal document?

This patch does too many things at once.  Split it up.  Also please
a delay between sending us patches.  Otherwise it's overwhelming to
deal with.  Bunch them together in a patchset instead of sending them
one by one.

regards,
dan carpenter