[PATCH] powerpc/pseries/papr-sysparm: use u8 arrays for payloads

[PATCH] powerpc/pseries/papr-sysparm: use u8 arrays for payloads

[Nathan Lynch via B4 Relay]

From: Nathan Lynch <nathanl@linux.ibm.com>

Some PAPR system parameter values are formatted by firmware as
nul-terminated strings (e.g. LPAR name, shared processor attributes).
But the values returned for other parameters, such as processor module
info and TLB block invalidate characteristics, are binary data with
parameter-specific layouts. So char[] isn't the appropriate type for
the general case. Use u8/__u8.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Fixes: 905b9e48786e ("powerpc/pseries/papr-sysparm: Expose character device to user space")
---
I'd like to get this in for v6.8 so the uapi header has the change for
its first point release.
---
 arch/powerpc/include/asm/papr-sysparm.h      | 2 +-
 arch/powerpc/include/uapi/asm/papr-sysparm.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/papr-sysparm.h b/arch/powerpc/include/asm/papr-sysparm.h
index 0dbbff59101d..c3cd5b131033 100644
--- a/arch/powerpc/include/asm/papr-sysparm.h
+++ b/arch/powerpc/include/asm/papr-sysparm.h
@@ -32,7 +32,7 @@ typedef struct {
  */
 struct papr_sysparm_buf {
 	__be16 len;
-	char val[PAPR_SYSPARM_MAX_OUTPUT];
+	u8 val[PAPR_SYSPARM_MAX_OUTPUT];
 };
 
 struct papr_sysparm_buf *papr_sysparm_buf_alloc(void);
diff --git a/arch/powerpc/include/uapi/asm/papr-sysparm.h b/arch/powerpc/include/uapi/asm/papr-sysparm.h
index 9f9a0f267ea5..f733467b1534 100644
--- a/arch/powerpc/include/uapi/asm/papr-sysparm.h
+++ b/arch/powerpc/include/uapi/asm/papr-sysparm.h
@@ -14,7 +14,7 @@ enum {
 struct papr_sysparm_io_block {
 	__u32 parameter;
 	__u16 length;
-	char data[PAPR_SYSPARM_MAX_OUTPUT];
+	__u8 data[PAPR_SYSPARM_MAX_OUTPUT];
 };
 
 /**

---
base-commit: 44a1aad2fe6c10bfe0589d8047057b10a4c18a19
change-id: 20240201-papr-sysparm-ioblock-data-use-u8-10d283cb6f1c

Best regards,
-- 
Nathan Lynch <nathanl@linux.ibm.com>

Re: [PATCH] powerpc/pseries/papr-sysparm: use u8 arrays for payloads

[Michael Ellerman]

On Fri, 02 Feb 2024 18:26:46 -0600, Nathan Lynch wrote:
> Some PAPR system parameter values are formatted by firmware as
> nul-terminated strings (e.g. LPAR name, shared processor attributes).
> But the values returned for other parameters, such as processor module
> info and TLB block invalidate characteristics, are binary data with
> parameter-specific layouts. So char[] isn't the appropriate type for
> the general case. Use u8/__u8.
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/pseries/papr-sysparm: use u8 arrays for payloads
      https://git.kernel.org/powerpc/c/8ded03ae48b3657e0fbca99d8a9d8fa1bfb8c9be

cheers