linux-kernel - Re: [RFC PATCH net-next 02/10] net: hibmcge: Add read/write registers supported through the bar space

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Message-ID: <20240805125558.GA2633937@kernel.org>
Date: Mon, 5 Aug 2024 13:55:58 +0100
From: Simon Horman <horms@...nel.org>
To: Jijie Shao <shaojijie@...wei.com>
Cc: yisen.zhuang@...wei.com, salil.mehta@...wei.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	shenjian15@...wei.com, wangpeiyang1@...wei.com,
	liuyonglong@...wei.com, sudongming1@...wei.com,
	xujunsheng@...wei.com, shiyongbang@...wei.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH net-next 02/10] net: hibmcge: Add read/write
 registers supported through the bar space

On Wed, Jul 31, 2024 at 05:42:37PM +0800, Jijie Shao wrote:
> Add support for to read and write registers through the pic bar space.
> 
> Some driver parameters, such as mac_id, are determined by the
> board form. Therefore, these parameters are initialized
> from the register as device specifications.
> 
> the device specifications register are initialized and writed by bmc.
> driver will read these registers when loading.
> 
> Signed-off-by: Jijie Shao <shaojijie@...wei.com>

...

> diff --git a/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h b/drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h

...

> +static inline void hbg_reg_write_field(struct hbg_priv *priv,  u32 reg_addr,
> +				       u32 mask, u32 val)
> +{
> +	u32 reg_value = hbg_reg_read(priv, reg_addr);
> +
> +	reg_value &= ~mask;
> +	reg_value |= FIELD_PREP(mask, val);

Hi,

I may well be wrong but I think that FIELD_PREP can only be used with
a compile-time constant as the mask.

In any case, with Clang-18 W=1 allmodconfig builds on x86_64 I see:

  CC      drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.o
   CC      drivers/net/ethernet/hisilicon/hibmcge/hbg_main.o
In file included from drivers/net/ethernet/hisilicon/hibmcge/hbg_main.c:8:
drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h:31:15: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigned short)0, short: (unsigned short)0, unsigned int: (unsigned int)0, int: (unsigned int)0, unsigned long: (unsigned long)0, long: (unsigned long)0, unsigned long long: (unsigned long long)0, long long: (unsigned long long)0, default: (mask)))' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
   31 |         reg_value |= FIELD_PREP(mask, val);
      |                      ^~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:115:3: note: expanded from macro 'FIELD_PREP'
  115 |                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:72:53: note: expanded from macro '__BF_FIELD_CHECK'
   72 |                 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
   73 |                                  __bf_cast_unsigned(_reg, ~0ull),       \
      |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   74 |                                  _pfx "type of reg too small for mask"); \
      |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
      |                                     ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
././include/linux/compiler_types.h:510:22: note: expanded from macro 'compiletime_assert'
  510 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |         ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:498:23: note: expanded from macro '_compiletime_assert'
  498 |         __compiletime_assert(condition, msg, prefix, suffix)
      |         ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:490:9: note: expanded from macro '__compiletime_assert'
  490 |                 if (!(condition))                                       \
      |                       ^~~~~~~~~
1 warning generated.
In file included from drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c:8:
drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h:31:15: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigned short)0, short: (unsigned short)0, unsigned int: (unsigned int)0, int: (unsigned int)0, unsigned long: (unsigned long)0, long: (unsigned long)0, unsigned long long: (unsigned long long)0, long long: (unsigned long long)0, default: (mask)))' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
   31 |         reg_value |= FIELD_PREP(mask, val);
      |                      ^~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:115:3: note: expanded from macro 'FIELD_PREP'
  115 |                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:72:53: note: expanded from macro '__BF_FIELD_CHECK'
   72 |                 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
   73 |                                  __bf_cast_unsigned(_reg, ~0ull),       \
      |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   74 |                                  _pfx "type of reg too small for mask"); \
      |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
      |                                     ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
././include/linux/compiler_types.h:510:22: note: expanded from macro 'compiletime_assert'
  510 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |         ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:498:23: note: expanded from macro '_compiletime_assert'
  498 |         __compiletime_assert(condition, msg, prefix, suffix)
      |         ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:490:9: note: expanded from macro '__compiletime_assert'
  490 |                 if (!(condition))                                       \
      |                       ^~~~~~~~~
1 warning generated.

...