linux-kernel - Re: [PATCH] crypto: ccree - avoid implicit enum conversion

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Message-ID: <20181017062202.yrwriuzsmbvgnapl@gondor.apana.org.au>
Date:   Wed, 17 Oct 2018 14:22:02 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Gilad Ben-Yossef <gilad@...yossef.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] crypto: ccree - avoid implicit enum conversion

On Wed, Oct 10, 2018 at 02:40:07PM -0700, Nathan Chancellor wrote:
> Clang warns when one enumerated type is implicitly converted to another
> and this happens in several locations in this driver, ultimately related
> to the set_cipher_{mode,config0} functions. set_cipher_mode expects a mode
> of type drv_cipher_mode and set_cipher_config0 expects a mode of type
> drv_crypto_direction.
> 
> drivers/crypto/ccree/cc_ivgen.c:58:35: warning: implicit conversion from
> enumeration type 'enum cc_desc_direction' to different enumeration type
> 'enum drv_crypto_direction' [-Wenum-conversion]
>         set_cipher_config0(&iv_seq[idx], DESC_DIRECTION_ENCRYPT_ENCRYPT);
> 
> drivers/crypto/ccree/cc_hash.c:99:28: warning: implicit conversion from
> enumeration type 'enum cc_hash_conf_pad' to different enumeration type
> 'enum drv_crypto_direction' [-Wenum-conversion]
>                 set_cipher_config0(desc, HASH_DIGEST_RESULT_LITTLE_ENDIAN);
> 
> drivers/crypto/ccree/cc_aead.c:1643:30: warning: implicit conversion
> from enumeration type 'enum drv_hash_hw_mode' to different enumeration
> type 'enum drv_cipher_mode' [-Wenum-conversion]
>         set_cipher_mode(&desc[idx], DRV_HASH_HW_GHASH);
> 
> Since this fundamentally isn't a problem because these values just
> represent simple integers for a shift operation, make it clear to Clang
> that this is okay by making the mode parameter in both functions an int.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/46
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
> 
> Alternatively:
> 
> 1. The uses of DESC_DIRECTION_ENCRYPT_ENCRYPT could be replaced with
>    DRV_CRYPTO_DIRECTION_ENCRYPT since they are the same value.
> 
> 2. An enum of value 2 could be added to drv_crypto_direction which is
>    what HASH_DIGEST_RESULT_LITTLE_ENDIAN is equal to (not sure what that
>    should be named).
> 
> 3. DRV_HASH_HW_GHASH could be removed and replaced with DRV_CIPHER_OFB
>    since they are the same value.
> 
> This patch seems to make the most sense to me given that the enums are
> just functioning as integers but I'm willing to fix this however the
> maintainers want.
> 
>  drivers/crypto/ccree/cc_hw_queue_defs.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt