The I3C abstraction expects u8 buffers, but some controllers operate with
a 32-bit bus width FIFO and cannot flag valid bytes individually. To avoid
reading or writing outside the buffer bounds, use 32-bit accesses where
possible and apply memcpy for any remaining bytes.

Add two auxiliary methods to include/linux/i3c/master.h and use in the dw
and cdns i3c controller drivers. The adi and renesas controller drivers
will also use these methods.

Related thread: https://lore.kernel.org/linux-i3c/aFNziEj7j31xy%2FmY@lizhi-Precision-Tower-5810/

Signed-off-by: Jorge Marques <jorge.marques@analog.com>
---
Changes in v3:
- Update i3c_writel_fifo/i3c_readl_fifo documentation
- Rename bytes to buffer
- Update cdns, dw commit messages
- Link to v2: https://lore.kernel.org/r/20250622-i3c-writesl-readsl-v2-0-2afd34ec6306@analog.com

Changes in v2:
- Rename to i3c_readl_fifo() and i3c_writel_fifo()
- Change type u8 *bytes to void *bytes
- Move methods to internals.h
- Reword commit messages to include new names and ().
- Fixup dw read fifo address (master -> master->reg)
- Link to v1: https://lore.kernel.org/r/20250620-i3c-writesl-readsl-v1-0-e0aa1c014dff@analog.com

---
Jorge Marques (3):
      i3c: master: Add inline i3c_readl_fifo() and i3c_writel_fifo()
      i3c: master: cdns: Use i3c_writel_fifo() and i3c_readl_fifo()
      i3c: master: dw: Use i3c_writel_fifo() and i3c_readl_fifo()

 drivers/i3c/internals.h              | 37 ++++++++++++++++++++++++++++++++++++
 drivers/i3c/master/dw-i3c-master.c   | 25 ++++--------------------
 drivers/i3c/master/i3c-master-cdns.c | 25 +++++-------------------
 3 files changed, 46 insertions(+), 41 deletions(-)
---
base-commit: 51963783b876a2f493a3eac0ea9eba271cb6809a
change-id: 20250620-i3c-writesl-readsl-e2836534b665

Best regards,
-- 
Jorge Marques <jorge.marques@analog.com>

On Tue, 24 Jun 2025 11:06:03 +0200, Jorge Marques wrote:
> The I3C abstraction expects u8 buffers, but some controllers operate with
> a 32-bit bus width FIFO and cannot flag valid bytes individually. To avoid
> reading or writing outside the buffer bounds, use 32-bit accesses where
> possible and apply memcpy for any remaining bytes.
> 
> Add two auxiliary methods to include/linux/i3c/master.h and use in the dw
> and cdns i3c controller drivers. The adi and renesas controller drivers
> will also use these methods.
> 
> [...]

Applied, thanks!

[1/3] i3c: master: Add inline i3c_readl_fifo() and i3c_writel_fifo()
      https://git.kernel.org/abelloni/c/733b439375b4
[2/3] i3c: master: cdns: Use i3c_writel_fifo() and i3c_readl_fifo()
      https://git.kernel.org/abelloni/c/c20d3fa70491
[3/3] i3c: master: dw: Use i3c_writel_fifo() and i3c_readl_fifo()
      https://git.kernel.org/abelloni/c/6e055b1fb2fc

Best regards,

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com