[PATCH v2] scsi: ufs: Fix the build for gcc 9 and before

[PATCH v2] scsi: ufs: Fix the build for gcc 9 and before

[Bart Van Assche]

gcc compilers before version 10 cannot do constant-folding for sub-byte
bitfields. This makes the compiler layout tests fail. Hence skip the
layout checks for gcc 9 and before.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/ufs/core/ufshcd.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 23335aaa6a66..4f5174735a4c 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -10564,6 +10564,14 @@ static const struct dev_pm_ops ufshcd_wl_pm_ops = {
 
 static void ufshcd_check_header_layout(void)
 {
+	/*
+	 * gcc compilers before version 10 cannot do constant-folding for
+	 * sub-byte bitfields. Hence skip the layout checks for gcc 9 and
+	 * before.
+	 */
+	if (IS_ENABLED(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 100000)
+		return;
+
 	BUILD_BUG_ON(((u8 *)&(struct request_desc_header){
 				.cci = 3})[0] != 3);
 

Re: [PATCH v2] scsi: ufs: Fix the build for gcc 9 and before

[Arnd Bergmann]

On Wed, Aug 2, 2023, at 01:21, Bart Van Assche wrote:
> gcc compilers before version 10 cannot do constant-folding for sub-byte
> bitfields. This makes the compiler layout tests fail. Hence skip the
> layout checks for gcc 9 and before.
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Looks good to me, I gave it a quick spin with
all versions from gcc-6 through gcc-10 to make sure this
works for all of them.
 
Tested-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH v2] scsi: ufs: Fix the build for gcc 9 and before

[Naresh Kamboju]

On Wed, 2 Aug 2023 at 12:18, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Aug 2, 2023, at 01:21, Bart Van Assche wrote:
> > gcc compilers before version 10 cannot do constant-folding for sub-byte
> > bitfields. This makes the compiler layout tests fail. Hence skip the
> > layout checks for gcc 9 and before.
> >
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> > Suggested-by: Arnd Bergmann <arnd@arndb.de>
> > Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Would it be a good idea to provide a link to the original report ?
Link: https://lore.kernel.org/linux-scsi/CA+G9fYur8UJoUyTLJFVEJPh-15TJ7kbdD2q8xVz8a3fLjkxxVw@mail.gmail.com/

>
> Looks good to me, I gave it a quick spin with
> all versions from gcc-6 through gcc-10 to make sure this
> works for all of them.
>
> Tested-by: Arnd Bergmann <arnd@arndb.de>

--
Linaro LKFT
https://lkft.linaro.org

Re: [PATCH v2] scsi: ufs: Fix the build for gcc 9 and before

[Martin K. Petersen]

Bart,

> gcc compilers before version 10 cannot do constant-folding for sub-byte
> bitfields. This makes the compiler layout tests fail. Hence skip the
> layout checks for gcc 9 and before.

Applied to 6.6/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering