[PATCH] riscv: hwcap: Don't alphabetize ISA extension IDs

[PATCH] riscv: hwcap: Don't alphabetize ISA extension IDs

[Andrew Jones]

While the comment above the ISA extension ID definitions says
"Entries are sorted alphabetically.", this stopped being good
advice with commit d8a3d8a75206 ("riscv: hwcap: make ISA extension
ids can be used in asm"), as we now use macros instead of enums.
Reshuffling defines is error-prone, so, since they don't need to be
in any particular order, change the advice to just adding new
extensions at the bottom. Also, take the opportunity to change
spaces to tabs, merge three comments into one, and move the base
and max defines into more logical locations wrt the ID definitions.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/include/asm/hwcap.h | 42 ++++++++++++++++------------------
 1 file changed, 20 insertions(+), 22 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index ee9c80fe0062..2a6dac9434b3 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -24,29 +24,27 @@
 #define RISCV_ISA_EXT_u		('u' - 'a')
 
 /*
- * Increse this to higher value as kernel support more ISA extensions.
- */
-#define RISCV_ISA_EXT_MAX	64
-#define RISCV_ISA_EXT_NAME_LEN_MAX 32
-
-/* The base ID for multi-letter ISA extensions */
-#define RISCV_ISA_EXT_BASE 26
-
-/*
- * These macros represent the logical ID for each multi-letter RISC-V ISA extension.
- * The logical ID should start from RISCV_ISA_EXT_BASE and must not exceed
- * RISCV_ISA_EXT_MAX. 0-25 range is reserved for single letter
- * extensions while all the multi-letter extensions should define the next
- * available logical extension id.
- * Entries are sorted alphabetically.
+ * These macros represent the logical IDs of each multi-letter RISC-V ISA
+ * extension and are used in the ISA bitmap. The logical IDs start from
+ * RISCV_ISA_EXT_BASE, which allows the 0-25 range to be reserved for single
+ * letter extensions. The maximum, RISCV_ISA_EXT_MAX, is defined in order
+ * to allocate the bitmap and may be increased when necessary.
+ *
+ * New extensions should just be added to the bottom, rather than added
+ * alphabetically, in order to avoid unnecessary shuffling.
  */
-#define RISCV_ISA_EXT_SSCOFPMF         26
-#define RISCV_ISA_EXT_SSTC             27
-#define RISCV_ISA_EXT_SVINVAL          28
-#define RISCV_ISA_EXT_SVPBMT           29
-#define RISCV_ISA_EXT_ZBB              30
-#define RISCV_ISA_EXT_ZICBOM           31
-#define RISCV_ISA_EXT_ZIHINTPAUSE      32
+#define RISCV_ISA_EXT_BASE		26
+
+#define RISCV_ISA_EXT_SSCOFPMF		26
+#define RISCV_ISA_EXT_SSTC		27
+#define RISCV_ISA_EXT_SVINVAL		28
+#define RISCV_ISA_EXT_SVPBMT		29
+#define RISCV_ISA_EXT_ZBB		30
+#define RISCV_ISA_EXT_ZICBOM		31
+#define RISCV_ISA_EXT_ZIHINTPAUSE	32
+
+#define RISCV_ISA_EXT_MAX		64
+#define RISCV_ISA_EXT_NAME_LEN_MAX	32
 
 #ifndef __ASSEMBLY__
 
-- 
2.39.1


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Re: [PATCH] riscv: hwcap: Don't alphabetize ISA extension IDs

[Conor Dooley]

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On Thu, Feb 09, 2023 at 01:36:36PM +0100, Andrew Jones wrote:
> While the comment above the ISA extension ID definitions says
> "Entries are sorted alphabetically.", this stopped being good
> advice with commit d8a3d8a75206 ("riscv: hwcap: make ISA extension
> ids can be used in asm"), as we now use macros instead of enums.

Yes, this ideally would have been removed by the commit doing the swap
over, but as both were in-flight simultaneously it was missed.
I intended going looking to see if this was dangling but clearly forgot.

> Reshuffling defines is error-prone, so, since they don't need to be
> in any particular order, change the advice to just adding new
> extensions at the bottom.

This aligns with what we "agreed" on Jisheng's patchset was the sanest
way to handle this.

> Also, take the opportunity to change
> spaces to tabs, merge three comments into one, and move the base
> and max defines into more logical locations wrt the ID definitions.

Sure, why not...

> Signed-off-by: Andrew Jones <ajones@ventanamicro.com>

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Thanks for fixing this up Drew!

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Re: [PATCH] riscv: hwcap: Don't alphabetize ISA extension IDs

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Thu,  9 Feb 2023 13:36:36 +0100 you wrote:
> While the comment above the ISA extension ID definitions says
> "Entries are sorted alphabetically.", this stopped being good
> advice with commit d8a3d8a75206 ("riscv: hwcap: make ISA extension
> ids can be used in asm"), as we now use macros instead of enums.
> Reshuffling defines is error-prone, so, since they don't need to be
> in any particular order, change the advice to just adding new
> extensions at the bottom. Also, take the opportunity to change
> spaces to tabs, merge three comments into one, and move the base
> and max defines into more logical locations wrt the ID definitions.
> 
> [...]

Here is the summary with links:
  - riscv: hwcap: Don't alphabetize ISA extension IDs
    https://git.kernel.org/riscv/c/dac8bf14bb49

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
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