Re: [PATCH] drm/xe: use %z format string for ptrdiff_t
From: Matt Roper
Date: Mon Mar 16 2026 - 18:51:36 EST
On Mon, Mar 16, 2026 at 11:43:46PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> ptrdiff_t, size_t and long are the same size on all supported architectures,
> but gcc requires the use of the %zx modifier instead of %lx. On 32-bit
Nathan Chancellor just sent a fix here:
https://lore.kernel.org/all/20260316-drm-xe-fix-32-bit-wformat-ptrdiff-v1-1-0108b10b2b6b@xxxxxxxxxx/
His solution uses %tx rather than %zx, which according to
Documentation/core-api/printk-formats.rst sounds like it's probably the
most accurate format string for this case?
Matt
> targets, the wrong one produces this warning:
>
> drivers/gpu/drm/xe/xe_lrc.c:1913:7: error: format specifies type 'unsigned long' but the argument has type '__ptrdiff_t' (aka 'int') [-Werror,-Wformat]
> 1912 | drm_printf(p, "LRC[%#5lx] = [%#010x] MI_NOOP (%d dwords)\n",
> | ~~~~~
> | %#5tx
> 1913 | dw - num_noop - start, inst_header, num_noop);
> | ^~~~~~~~~~~~~~~~~~~~~
>
> Fixes: 65fcf19cb36b ("drm/xe: Include running dword offset in default_lrc dumps")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> drivers/gpu/drm/xe/xe_lrc.c | 30 +++++++++++++++---------------
> 1 file changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
> index 5ab088e5e13d..c528818e8853 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.c
> +++ b/drivers/gpu/drm/xe/xe_lrc.c
> @@ -1909,17 +1909,17 @@ static int dump_mi_command(struct drm_printer *p,
> while (num_noop < remaining_dw &&
> (*(++dw) & REG_GENMASK(31, 23)) == MI_NOOP)
> num_noop++;
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_NOOP (%d dwords)\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_NOOP (%d dwords)\n",
> dw - num_noop - start, inst_header, num_noop);
> return num_noop;
>
> case MI_TOPOLOGY_FILTER:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_TOPOLOGY_FILTER\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_TOPOLOGY_FILTER\n",
> dw - start, inst_header);
> return 1;
>
> case MI_BATCH_BUFFER_END:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_BATCH_BUFFER_END\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_BATCH_BUFFER_END\n",
> dw - start, inst_header);
> /* Return 'remaining_dw' to consume the rest of the LRC */
> return remaining_dw;
> @@ -1934,35 +1934,35 @@ static int dump_mi_command(struct drm_printer *p,
>
> switch (inst_header & MI_OPCODE) {
> case MI_LOAD_REGISTER_IMM:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_LOAD_REGISTER_IMM: %d regs\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_LOAD_REGISTER_IMM: %d regs\n",
> dw - start, inst_header, (numdw - 1) / 2);
> for (int i = 1; i < numdw; i += 2)
> - drm_printf(p, "LRC[%#5lx] = - %#6x = %#010x\n",
> + drm_printf(p, "LRC[%#5zx] = - %#6x = %#010x\n",
> &dw[i] - start, dw[i], dw[i + 1]);
> return numdw;
>
> case MI_LOAD_REGISTER_MEM & MI_OPCODE:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_LOAD_REGISTER_MEM: %s%s\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_LOAD_REGISTER_MEM: %s%s\n",
> dw - start, inst_header,
> dw[0] & MI_LRI_LRM_CS_MMIO ? "CS_MMIO " : "",
> dw[0] & MI_LRM_USE_GGTT ? "USE_GGTT " : "");
> if (numdw == 4)
> - drm_printf(p, "LRC[%#5lx] = - %#6x = %#010llx\n",
> + drm_printf(p, "LRC[%#5zx] = - %#6x = %#010llx\n",
> dw - start,
> dw[1], ((u64)(dw[3]) << 32 | (u64)(dw[2])));
> else
> - drm_printf(p, "LRC[%#5lx] = - %*ph (%s)\n",
> + drm_printf(p, "LRC[%#5zx] = - %*ph (%s)\n",
> dw - start, (int)sizeof(u32) * (numdw - 1),
> dw + 1, numdw < 4 ? "truncated" : "malformed");
> return numdw;
>
> case MI_FORCE_WAKEUP:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] MI_FORCE_WAKEUP\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] MI_FORCE_WAKEUP\n",
> dw - start, inst_header);
> return numdw;
>
> default:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] unknown MI opcode %#x, likely %d dwords\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] unknown MI opcode %#x, likely %d dwords\n",
> dw - start, inst_header, opcode, numdw);
> return numdw;
> }
> @@ -1989,12 +1989,12 @@ static int dump_gfxpipe_command(struct drm_printer *p,
> switch (*dw & GFXPIPE_MATCH_MASK) {
> #define MATCH(cmd) \
> case cmd: \
> - drm_printf(p, "LRC[%#5lx] = [%#010x] " #cmd " (%d dwords)\n", \
> + drm_printf(p, "LRC[%#5zx] = [%#010x] " #cmd " (%d dwords)\n", \
> dw - start, *dw, numdw); \
> return numdw
> #define MATCH3D(cmd) \
> case CMD_##cmd: \
> - drm_printf(p, "LRC[%#5lx] = [%#010x] " #cmd " (%d dwords)\n", \
> + drm_printf(p, "LRC[%#5zx] = [%#010x] " #cmd " (%d dwords)\n", \
> dw - start, *dw, numdw); \
> return numdw
>
> @@ -2127,7 +2127,7 @@ static int dump_gfxpipe_command(struct drm_printer *p,
> MATCH3D(3DSTATE_SLICE_TABLE_STATE_POINTER_2);
>
> default:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] unknown GFXPIPE command (pipeline=%#x, opcode=%#x, subopcode=%#x), likely %d dwords\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] unknown GFXPIPE command (pipeline=%#x, opcode=%#x, subopcode=%#x), likely %d dwords\n",
> dw - start, *dw, pipeline, opcode, subopcode, numdw);
> return numdw;
> }
> @@ -2153,7 +2153,7 @@ static int dump_gfx_state_command(struct drm_printer *p,
> MATCH(STATE_WRITE_INLINE);
>
> default:
> - drm_printf(p, "LRC[%#5lx] = [%#010x] unknown GFX_STATE command (opcode=%#x), likely %d dwords\n",
> + drm_printf(p, "LRC[%#5zx] = [%#010x] unknown GFX_STATE command (opcode=%#x), likely %d dwords\n",
> dw - start, *dw, opcode, numdw);
> return numdw;
> }
> @@ -2188,7 +2188,7 @@ void xe_lrc_dump_default(struct drm_printer *p,
> num_dw = dump_gfx_state_command(p, gt, start, dw, remaining_dw);
> } else {
> num_dw = min(instr_dw(*dw), remaining_dw);
> - drm_printf(p, "LRC[%#5lx] = [%#10x] Unknown instruction of type %#x, likely %d dwords\n",
> + drm_printf(p, "LRC[%#5zx] = [%#10x] Unknown instruction of type %#x, likely %d dwords\n",
> dw - start,
> *dw, REG_FIELD_GET(XE_INSTR_CMD_TYPE, *dw),
> num_dw);
> --
> 2.39.5
>
--
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation