* drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
@ 2020-11-02 4:42 kernel test robot
2020-11-10 11:38 ` Serge Semin
0 siblings, 1 reply; 12+ messages in thread
From: kernel test robot @ 2020-11-02 4:42 UTC (permalink / raw)
To: Serge Semin; +Cc: kbuild-all, linux-kernel, Miquel Raynal
[-- Attachment #1: Type: text/plain, Size: 2837 bytes --]
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 3cea11cd5e3b00d91caf0b4730194039b45c5891
commit: b3e79e7682e075326df8041b826b03453acacd0a mtd: physmap: Add Baikal-T1 physically mapped ROM support
date: 4 weeks ago
config: sparc64-randconfig-s032-20201031 (attached as .config)
compiler: sparc64-linux-gcc (GCC) 9.3.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.3-76-gf680124b-dirty
# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3e79e7682e075326df8041b826b03453acacd0a
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout b3e79e7682e075326df8041b826b03453acacd0a
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=sparc64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
"sparse warnings: (new ones prefixed by >>)"
>> drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
vim +/__iomem +78 drivers/mtd/maps/physmap-bt1-rom.c
57
58 static void __xipram bt1_rom_map_copy_from(struct map_info *map,
59 void *to, unsigned long from,
60 ssize_t len)
61 {
62 void __iomem *src = map->virt + from;
63 ssize_t shift, chunk;
64 u32 data;
65
66 if (len <= 0 || from >= map->size)
67 return;
68
69 /* Make sure we don't go over the map limit. */
70 len = min_t(ssize_t, map->size - from, len);
71
72 /*
73 * Since requested data size can be pretty big we have to implement
74 * the copy procedure as optimal as possible. That's why it's split
75 * up into the next three stages: unaligned head, aligned body,
76 * unaligned tail.
77 */
> 78 shift = (ssize_t)src & 0x3;
79 if (shift) {
80 chunk = min_t(ssize_t, 4 - shift, len);
81 data = readl_relaxed(src - shift);
82 memcpy(to, &data + shift, chunk);
83 src += chunk;
84 to += chunk;
85 len -= chunk;
86 }
87
88 while (len >= 4) {
89 data = readl_relaxed(src);
90 memcpy(to, &data, 4);
91 src += 4;
92 to += 4;
93 len -= 4;
94 }
95
96 if (len) {
97 data = readl_relaxed(src);
98 memcpy(to, &data, len);
99 }
100 }
101
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 36802 bytes --]
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-02 4:42 drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression kernel test robot
@ 2020-11-10 11:38 ` Serge Semin
2020-11-10 15:35 ` Miquel Raynal
0 siblings, 1 reply; 12+ messages in thread
From: Serge Semin @ 2020-11-10 11:38 UTC (permalink / raw)
To: Miquel Raynal; +Cc: kernel test robot, kbuild-all, linux-kernel, linux-mtd
Hello Miquel,
A situation noted by the warning below won't cause any problem because
the casting is done to a non-dereferenced variable. It is utilized
as a pointer bias later in that function. Shall we just ignore the
warning or still fix it somehow?
-Sergey
On Mon, Nov 02, 2020 at 12:42:57PM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 3cea11cd5e3b00d91caf0b4730194039b45c5891
> commit: b3e79e7682e075326df8041b826b03453acacd0a mtd: physmap: Add Baikal-T1 physically mapped ROM support
> date: 4 weeks ago
> config: sparc64-randconfig-s032-20201031 (attached as .config)
> compiler: sparc64-linux-gcc (GCC) 9.3.0
> reproduce:
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # apt-get install sparse
> # sparse version: v0.6.3-76-gf680124b-dirty
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b3e79e7682e075326df8041b826b03453acacd0a
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git fetch --no-tags linus master
> git checkout b3e79e7682e075326df8041b826b03453acacd0a
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=sparc64
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
>
> "sparse warnings: (new ones prefixed by >>)"
> >> drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
>
> vim +/__iomem +78 drivers/mtd/maps/physmap-bt1-rom.c
>
> 57
> 58 static void __xipram bt1_rom_map_copy_from(struct map_info *map,
> 59 void *to, unsigned long from,
> 60 ssize_t len)
> 61 {
> 62 void __iomem *src = map->virt + from;
> 63 ssize_t shift, chunk;
> 64 u32 data;
> 65
> 66 if (len <= 0 || from >= map->size)
> 67 return;
> 68
> 69 /* Make sure we don't go over the map limit. */
> 70 len = min_t(ssize_t, map->size - from, len);
> 71
> 72 /*
> 73 * Since requested data size can be pretty big we have to implement
> 74 * the copy procedure as optimal as possible. That's why it's split
> 75 * up into the next three stages: unaligned head, aligned body,
> 76 * unaligned tail.
> 77 */
> > 78 shift = (ssize_t)src & 0x3;
> 79 if (shift) {
> 80 chunk = min_t(ssize_t, 4 - shift, len);
> 81 data = readl_relaxed(src - shift);
> 82 memcpy(to, &data + shift, chunk);
> 83 src += chunk;
> 84 to += chunk;
> 85 len -= chunk;
> 86 }
> 87
> 88 while (len >= 4) {
> 89 data = readl_relaxed(src);
> 90 memcpy(to, &data, 4);
> 91 src += 4;
> 92 to += 4;
> 93 len -= 4;
> 94 }
> 95
> 96 if (len) {
> 97 data = readl_relaxed(src);
> 98 memcpy(to, &data, len);
> 99 }
> 100 }
> 101
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-10 11:38 ` Serge Semin
@ 2020-11-10 15:35 ` Miquel Raynal
2020-11-11 19:22 ` Serge Semin
0 siblings, 1 reply; 12+ messages in thread
From: Miquel Raynal @ 2020-11-10 15:35 UTC (permalink / raw)
To: Serge Semin; +Cc: kernel test robot, kbuild-all, linux-kernel, linux-mtd
Hi Serge,
Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
2020 14:38:27 +0300:
> Hello Miquel,
>
> A situation noted by the warning below won't cause any problem because
> the casting is done to a non-dereferenced variable. It is utilized
> as a pointer bias later in that function. Shall we just ignore the
> warning or still fix it somehow?
Do you think the cast to a !__iomem value is mandatory here?
Perhaps if you find an elegant wait to avoid the warning it would be
nice, otherwise I guess we'll let it aside as a false positive.
Cheers,
Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-10 15:35 ` Miquel Raynal
@ 2020-11-11 19:22 ` Serge Semin
2020-11-12 8:27 ` Miquel Raynal
0 siblings, 1 reply; 12+ messages in thread
From: Serge Semin @ 2020-11-11 19:22 UTC (permalink / raw)
To: Miquel Raynal
Cc: Serge Semin, kernel test robot, kbuild-all, linux-kernel, linux-mtd
On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> Hi Serge,
>
> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> 2020 14:38:27 +0300:
>
> > Hello Miquel,
> >
> > A situation noted by the warning below won't cause any problem because
> > the casting is done to a non-dereferenced variable. It is utilized
> > as a pointer bias later in that function. Shall we just ignore the
> > warning or still fix it somehow?
>
> Do you think the cast to a !__iomem value is mandatory here?
It's not mandatory to have the casting with no __iomem, but wouldn't
doing like this:
+ shift = (ssize_t __iomem)src & 0x3;
be looking weird? Really, is there a good way to somehow extract the first
two bits of a __iomem pointer without getting the sparse warning?
-Sergey
>
> Perhaps if you find an elegant wait to avoid the warning it would be
> nice, otherwise I guess we'll let it aside as a false positive.
>
> Cheers,
> Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-11 19:22 ` Serge Semin
@ 2020-11-12 8:27 ` Miquel Raynal
2020-11-12 11:20 ` Serge Semin
2020-11-12 15:00 ` Vignesh Raghavendra
0 siblings, 2 replies; 12+ messages in thread
From: Miquel Raynal @ 2020-11-12 8:27 UTC (permalink / raw)
To: Serge Semin
Cc: Serge Semin, kernel test robot, kbuild-all, linux-kernel, linux-mtd
Hi Sergey,
Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
2020 22:22:59 +0300:
> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > Hi Serge,
> >
> > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > 2020 14:38:27 +0300:
> >
> > > Hello Miquel,
> > >
> > > A situation noted by the warning below won't cause any problem because
> > > the casting is done to a non-dereferenced variable. It is utilized
> > > as a pointer bias later in that function. Shall we just ignore the
> > > warning or still fix it somehow?
> >
>
> > Do you think the cast to a !__iomem value is mandatory here?
>
> It's not mandatory to have the casting with no __iomem, but wouldn't
> doing like this:
> + shift = (ssize_t __iomem)src & 0x3;
> be looking weird? Really, is there a good way to somehow extract the first
> two bits of a __iomem pointer without getting the sparse warning?
I asked around me, what about trying uintptr_t?
Thanks,
Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 8:27 ` Miquel Raynal
@ 2020-11-12 11:20 ` Serge Semin
2020-11-12 15:00 ` Vignesh Raghavendra
1 sibling, 0 replies; 12+ messages in thread
From: Serge Semin @ 2020-11-12 11:20 UTC (permalink / raw)
To: Miquel Raynal
Cc: Serge Semin, kernel test robot, kbuild-all, linux-kernel, linux-mtd
On Thu, Nov 12, 2020 at 09:27:15AM +0100, Miquel Raynal wrote:
> Hi Sergey,
>
> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> 2020 22:22:59 +0300:
>
> > On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > > Hi Serge,
> > >
> > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > > 2020 14:38:27 +0300:
> > >
> > > > Hello Miquel,
> > > >
> > > > A situation noted by the warning below won't cause any problem because
> > > > the casting is done to a non-dereferenced variable. It is utilized
> > > > as a pointer bias later in that function. Shall we just ignore the
> > > > warning or still fix it somehow?
> > >
> >
> > > Do you think the cast to a !__iomem value is mandatory here?
> >
> > It's not mandatory to have the casting with no __iomem, but wouldn't
> > doing like this:
> > + shift = (ssize_t __iomem)src & 0x3;
> > be looking weird? Really, is there a good way to somehow extract the first
> > two bits of a __iomem pointer without getting the sparse warning?
>
> I asked around me, what about trying uintptr_t?
Hm, that's weird. sparse gets happy if a casting to an unsigned type
is used here. That's why the similar statement defined in
bt1_rom_map_read() doesn't cause the sparse warning, while the
statement with ssize_t does.
Can people around explain whether that is just an internal sparse
feature or there is a particular reason of having the unsigned types
casting ignored by sparse in this case? I don't really understand why
removing the __iomem attribute with casting to a signed type cause the
warning, while casting to an unsigned type doesn't...
Anyway I'll send a patch with the fix of using the uintptr_t casting
here. Thanks for suggesting the solution.
-Sergey
>
> Thanks,
> Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 8:27 ` Miquel Raynal
2020-11-12 11:20 ` Serge Semin
@ 2020-11-12 15:00 ` Vignesh Raghavendra
2020-11-12 15:27 ` Serge Semin
1 sibling, 1 reply; 12+ messages in thread
From: Vignesh Raghavendra @ 2020-11-12 15:00 UTC (permalink / raw)
To: Miquel Raynal, Serge Semin
Cc: linux-mtd, kbuild-all, kernel test robot, Serge Semin, linux-kernel
On 11/12/20 1:57 PM, Miquel Raynal wrote:
> Hi Sergey,
>
> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> 2020 22:22:59 +0300:
>
>> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
>>> Hi Serge,
>>>
>>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
>>> 2020 14:38:27 +0300:
>>>
>>>> Hello Miquel,
>>>>
>>>> A situation noted by the warning below won't cause any problem because
>>>> the casting is done to a non-dereferenced variable. It is utilized
>>>> as a pointer bias later in that function. Shall we just ignore the
>>>> warning or still fix it somehow?
>>>
>>
>>> Do you think the cast to a !__iomem value is mandatory here?
>>
>> It's not mandatory to have the casting with no __iomem, but wouldn't
>> doing like this:
>> + shift = (ssize_t __iomem)src & 0x3;
>> be looking weird? Really, is there a good way to somehow extract the first
>> two bits of a __iomem pointer without getting the sparse warning?
>
> I asked around me, what about trying uintptr_t?
>
One more way is to use __force to tell sparse that this casting is
intentional:
shift = (__force ssize_t)src & 0x3;
> Thanks,
> Miquèl
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 15:00 ` Vignesh Raghavendra
@ 2020-11-12 15:27 ` Serge Semin
2020-11-12 15:43 ` Miquel Raynal
0 siblings, 1 reply; 12+ messages in thread
From: Serge Semin @ 2020-11-12 15:27 UTC (permalink / raw)
To: Vignesh Raghavendra
Cc: Serge Semin, Miquel Raynal, linux-mtd, kbuild-all,
kernel test robot, linux-kernel
Hello Vignesh
On Thu, Nov 12, 2020 at 08:30:42PM +0530, Vignesh Raghavendra wrote:
>
>
> On 11/12/20 1:57 PM, Miquel Raynal wrote:
> > Hi Sergey,
> >
> > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> > 2020 22:22:59 +0300:
> >
> >> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> >>> Hi Serge,
> >>>
> >>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> >>> 2020 14:38:27 +0300:
> >>>
> >>>> Hello Miquel,
> >>>>
> >>>> A situation noted by the warning below won't cause any problem because
> >>>> the casting is done to a non-dereferenced variable. It is utilized
> >>>> as a pointer bias later in that function. Shall we just ignore the
> >>>> warning or still fix it somehow?
> >>>
> >>
> >>> Do you think the cast to a !__iomem value is mandatory here?
> >>
> >> It's not mandatory to have the casting with no __iomem, but wouldn't
> >> doing like this:
> >> + shift = (ssize_t __iomem)src & 0x3;
> >> be looking weird? Really, is there a good way to somehow extract the first
> >> two bits of a __iomem pointer without getting the sparse warning?
> >
> > I asked around me, what about trying uintptr_t?
> >
>
> One more way is to use __force to tell sparse that this casting is
> intentional:
>
> shift = (__force ssize_t)src & 0x3;
Oh, great! That solution is actually much better than using some
currently unexplained sparse peculiarity! I was thinking about applying
some other attribute, but __force just didn't come to my mind. Thank
you very much for the suggestion. I'll post the fix with the solution
suggested by you.
-Sergey
>
>
> > Thanks,
> > Miquèl
> >
> > ______________________________________________________
> > Linux MTD discussion mailing list
> > http://lists.infradead.org/mailman/listinfo/linux-mtd/
> >
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 15:27 ` Serge Semin
@ 2020-11-12 15:43 ` Miquel Raynal
2020-11-12 16:10 ` Serge Semin
0 siblings, 1 reply; 12+ messages in thread
From: Miquel Raynal @ 2020-11-12 15:43 UTC (permalink / raw)
To: Serge Semin
Cc: Vignesh Raghavendra, Serge Semin, linux-mtd, kbuild-all,
kernel test robot, linux-kernel
Hi Serge,
Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
2020 18:27:39 +0300:
> Hello Vignesh
>
> On Thu, Nov 12, 2020 at 08:30:42PM +0530, Vignesh Raghavendra wrote:
> >
> >
> > On 11/12/20 1:57 PM, Miquel Raynal wrote:
> > > Hi Sergey,
> > >
> > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> > > 2020 22:22:59 +0300:
> > >
> > >> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > >>> Hi Serge,
> > >>>
> > >>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > >>> 2020 14:38:27 +0300:
> > >>>
> > >>>> Hello Miquel,
> > >>>>
> > >>>> A situation noted by the warning below won't cause any problem because
> > >>>> the casting is done to a non-dereferenced variable. It is utilized
> > >>>> as a pointer bias later in that function. Shall we just ignore the
> > >>>> warning or still fix it somehow?
> > >>>
> > >>
> > >>> Do you think the cast to a !__iomem value is mandatory here?
> > >>
> > >> It's not mandatory to have the casting with no __iomem, but wouldn't
> > >> doing like this:
> > >> + shift = (ssize_t __iomem)src & 0x3;
> > >> be looking weird? Really, is there a good way to somehow extract the first
> > >> two bits of a __iomem pointer without getting the sparse warning?
> > >
> > > I asked around me, what about trying uintptr_t?
> > >
> >
>
> > One more way is to use __force to tell sparse that this casting is
> > intentional:
> >
> > shift = (__force ssize_t)src & 0x3;
>
> Oh, great! That solution is actually much better than using some
> currently unexplained sparse peculiarity! I was thinking about applying
> some other attribute, but __force just didn't come to my mind. Thank
> you very much for the suggestion. I'll post the fix with the solution
> suggested by you.
Is the ssize_t cast the right one btw? I would definitely prefer an
unsigned type here.
Thanks,
Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 15:43 ` Miquel Raynal
@ 2020-11-12 16:10 ` Serge Semin
2020-11-12 16:15 ` Miquel Raynal
0 siblings, 1 reply; 12+ messages in thread
From: Serge Semin @ 2020-11-12 16:10 UTC (permalink / raw)
To: Miquel Raynal
Cc: Serge Semin, Vignesh Raghavendra, linux-mtd, kbuild-all,
kernel test robot, linux-kernel
On Thu, Nov 12, 2020 at 04:43:01PM +0100, Miquel Raynal wrote:
> Hi Serge,
>
> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
> 2020 18:27:39 +0300:
>
> > Hello Vignesh
> >
> > On Thu, Nov 12, 2020 at 08:30:42PM +0530, Vignesh Raghavendra wrote:
> > >
> > >
> > > On 11/12/20 1:57 PM, Miquel Raynal wrote:
> > > > Hi Sergey,
> > > >
> > > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> > > > 2020 22:22:59 +0300:
> > > >
> > > >> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > > >>> Hi Serge,
> > > >>>
> > > >>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > > >>> 2020 14:38:27 +0300:
> > > >>>
> > > >>>> Hello Miquel,
> > > >>>>
> > > >>>> A situation noted by the warning below won't cause any problem because
> > > >>>> the casting is done to a non-dereferenced variable. It is utilized
> > > >>>> as a pointer bias later in that function. Shall we just ignore the
> > > >>>> warning or still fix it somehow?
> > > >>>
> > > >>
> > > >>> Do you think the cast to a !__iomem value is mandatory here?
> > > >>
> > > >> It's not mandatory to have the casting with no __iomem, but wouldn't
> > > >> doing like this:
> > > >> + shift = (ssize_t __iomem)src & 0x3;
> > > >> be looking weird? Really, is there a good way to somehow extract the first
> > > >> two bits of a __iomem pointer without getting the sparse warning?
> > > >
> > > > I asked around me, what about trying uintptr_t?
> > > >
> > >
> >
> > > One more way is to use __force to tell sparse that this casting is
> > > intentional:
> > >
> > > shift = (__force ssize_t)src & 0x3;
> >
> > Oh, great! That solution is actually much better than using some
> > currently unexplained sparse peculiarity! I was thinking about applying
> > some other attribute, but __force just didn't come to my mind. Thank
> > you very much for the suggestion. I'll post the fix with the solution
> > suggested by you.
>
> Is the ssize_t cast the right one btw? I would definitely prefer an
> unsigned type here.
The reason of me deciding to use the ssize_t type here was to prevent
the types casting across the "shift", "chunk" and "len" variables
within this method. It seemed a bit better than having a standard type
like "unsigned int" here seeing the ssize_t type width won't exceed
the long type size anyway. Moreover since the "len" variable has got
the ssize_t type and I couldn't change it (the method is the map_info
callback), I've decided to stick with what is available and defined
"shift" and "chunk" as ssize_t-es. Another callback method
bt1_rom_map_read() in his module has been designed in the same way.
Do you think it's better to change it in favor of using a different
type like "unsigned int" here anyway? If so for unification I'd need to
change bt1_rom_map_read() (though the "shift" variable has been
defined as "unsigned long" there in the first place because the offs
argument has got that type).
What to do with the __force attribute here? It does seem appropriate
even if for some mystical reasons we haven't got the sparse warning
for the unsigned types.
-Sergey
>
> Thanks,
> Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 16:10 ` Serge Semin
@ 2020-11-12 16:15 ` Miquel Raynal
2020-11-12 16:21 ` Serge Semin
0 siblings, 1 reply; 12+ messages in thread
From: Miquel Raynal @ 2020-11-12 16:15 UTC (permalink / raw)
To: Serge Semin
Cc: Serge Semin, Vignesh Raghavendra, linux-mtd, kbuild-all,
kernel test robot, linux-kernel
Hi Serge,
Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
2020 19:10:43 +0300:
> On Thu, Nov 12, 2020 at 04:43:01PM +0100, Miquel Raynal wrote:
> > Hi Serge,
> >
> > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
> > 2020 18:27:39 +0300:
> >
> > > Hello Vignesh
> > >
> > > On Thu, Nov 12, 2020 at 08:30:42PM +0530, Vignesh Raghavendra wrote:
> > > >
> > > >
> > > > On 11/12/20 1:57 PM, Miquel Raynal wrote:
> > > > > Hi Sergey,
> > > > >
> > > > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> > > > > 2020 22:22:59 +0300:
> > > > >
> > > > >> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > > > >>> Hi Serge,
> > > > >>>
> > > > >>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > > > >>> 2020 14:38:27 +0300:
> > > > >>>
> > > > >>>> Hello Miquel,
> > > > >>>>
> > > > >>>> A situation noted by the warning below won't cause any problem because
> > > > >>>> the casting is done to a non-dereferenced variable. It is utilized
> > > > >>>> as a pointer bias later in that function. Shall we just ignore the
> > > > >>>> warning or still fix it somehow?
> > > > >>>
> > > > >>
> > > > >>> Do you think the cast to a !__iomem value is mandatory here?
> > > > >>
> > > > >> It's not mandatory to have the casting with no __iomem, but wouldn't
> > > > >> doing like this:
> > > > >> + shift = (ssize_t __iomem)src & 0x3;
> > > > >> be looking weird? Really, is there a good way to somehow extract the first
> > > > >> two bits of a __iomem pointer without getting the sparse warning?
> > > > >
> > > > > I asked around me, what about trying uintptr_t?
> > > > >
> > > >
> > >
> > > > One more way is to use __force to tell sparse that this casting is
> > > > intentional:
> > > >
> > > > shift = (__force ssize_t)src & 0x3;
> > >
> > > Oh, great! That solution is actually much better than using some
> > > currently unexplained sparse peculiarity! I was thinking about applying
> > > some other attribute, but __force just didn't come to my mind. Thank
> > > you very much for the suggestion. I'll post the fix with the solution
> > > suggested by you.
> >
>
> > Is the ssize_t cast the right one btw? I would definitely prefer an
> > unsigned type here.
>
> The reason of me deciding to use the ssize_t type here was to prevent
> the types casting across the "shift", "chunk" and "len" variables
> within this method. It seemed a bit better than having a standard type
> like "unsigned int" here seeing the ssize_t type width won't exceed
> the long type size anyway. Moreover since the "len" variable has got
> the ssize_t type and I couldn't change it (the method is the map_info
> callback), I've decided to stick with what is available and defined
> "shift" and "chunk" as ssize_t-es. Another callback method
> bt1_rom_map_read() in his module has been designed in the same way.
>
> Do you think it's better to change it in favor of using a different
> type like "unsigned int" here anyway?
I would say yes.
> If so for unification I'd need to
> change bt1_rom_map_read() (though the "shift" variable has been
> defined as "unsigned long" there in the first place because the offs
> argument has got that type).
Fine.
>
> What to do with the __force attribute here? It does seem appropriate
> even if for some mystical reasons we haven't got the sparse warning
> for the unsigned types.
Yeah this is strange. I would, however, suggest not to add this keyword
if we don't need it.
Thanks,
Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression
2020-11-12 16:15 ` Miquel Raynal
@ 2020-11-12 16:21 ` Serge Semin
0 siblings, 0 replies; 12+ messages in thread
From: Serge Semin @ 2020-11-12 16:21 UTC (permalink / raw)
To: Miquel Raynal
Cc: Vignesh Raghavendra, linux-mtd, kbuild-all, kernel test robot,
linux-kernel
On Thu, Nov 12, 2020 at 05:15:10PM +0100, Miquel Raynal wrote:
> Hi Serge,
>
> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
> 2020 19:10:43 +0300:
>
> > On Thu, Nov 12, 2020 at 04:43:01PM +0100, Miquel Raynal wrote:
> > > Hi Serge,
> > >
> > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Thu, 12 Nov
> > > 2020 18:27:39 +0300:
> > >
> > > > Hello Vignesh
> > > >
> > > > On Thu, Nov 12, 2020 at 08:30:42PM +0530, Vignesh Raghavendra wrote:
> > > > >
> > > > >
> > > > > On 11/12/20 1:57 PM, Miquel Raynal wrote:
> > > > > > Hi Sergey,
> > > > > >
> > > > > > Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Wed, 11 Nov
> > > > > > 2020 22:22:59 +0300:
> > > > > >
> > > > > >> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > > > > >>> Hi Serge,
> > > > > >>>
> > > > > >>> Serge Semin <Sergey.Semin@baikalelectronics.ru> wrote on Tue, 10 Nov
> > > > > >>> 2020 14:38:27 +0300:
> > > > > >>>
> > > > > >>>> Hello Miquel,
> > > > > >>>>
> > > > > >>>> A situation noted by the warning below won't cause any problem because
> > > > > >>>> the casting is done to a non-dereferenced variable. It is utilized
> > > > > >>>> as a pointer bias later in that function. Shall we just ignore the
> > > > > >>>> warning or still fix it somehow?
> > > > > >>>
> > > > > >>
> > > > > >>> Do you think the cast to a !__iomem value is mandatory here?
> > > > > >>
> > > > > >> It's not mandatory to have the casting with no __iomem, but wouldn't
> > > > > >> doing like this:
> > > > > >> + shift = (ssize_t __iomem)src & 0x3;
> > > > > >> be looking weird? Really, is there a good way to somehow extract the first
> > > > > >> two bits of a __iomem pointer without getting the sparse warning?
> > > > > >
> > > > > > I asked around me, what about trying uintptr_t?
> > > > > >
> > > > >
> > > >
> > > > > One more way is to use __force to tell sparse that this casting is
> > > > > intentional:
> > > > >
> > > > > shift = (__force ssize_t)src & 0x3;
> > > >
> > > > Oh, great! That solution is actually much better than using some
> > > > currently unexplained sparse peculiarity! I was thinking about applying
> > > > some other attribute, but __force just didn't come to my mind. Thank
> > > > you very much for the suggestion. I'll post the fix with the solution
> > > > suggested by you.
> > >
> >
> > > Is the ssize_t cast the right one btw? I would definitely prefer an
> > > unsigned type here.
> >
> > The reason of me deciding to use the ssize_t type here was to prevent
> > the types casting across the "shift", "chunk" and "len" variables
> > within this method. It seemed a bit better than having a standard type
> > like "unsigned int" here seeing the ssize_t type width won't exceed
> > the long type size anyway. Moreover since the "len" variable has got
> > the ssize_t type and I couldn't change it (the method is the map_info
> > callback), I've decided to stick with what is available and defined
> > "shift" and "chunk" as ssize_t-es. Another callback method
> > bt1_rom_map_read() in his module has been designed in the same way.
> >
> > Do you think it's better to change it in favor of using a different
> > type like "unsigned int" here anyway?
>
> I would say yes.
>
> > If so for unification I'd need to
> > change bt1_rom_map_read() (though the "shift" variable has been
> > defined as "unsigned long" there in the first place because the offs
> > argument has got that type).
>
> Fine.
>
> >
> > What to do with the __force attribute here? It does seem appropriate
> > even if for some mystical reasons we haven't got the sparse warning
> > for the unsigned types.
>
> Yeah this is strange. I would, however, suggest not to add this keyword
> if we don't need it.
Ok. "unsigned int" it is then.
-Sergey
>
> Thanks,
> Miquèl
^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2020-11-12 16:22 UTC | newest]
Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-02 4:42 drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '__iomem' of expression kernel test robot
2020-11-10 11:38 ` Serge Semin
2020-11-10 15:35 ` Miquel Raynal
2020-11-11 19:22 ` Serge Semin
2020-11-12 8:27 ` Miquel Raynal
2020-11-12 11:20 ` Serge Semin
2020-11-12 15:00 ` Vignesh Raghavendra
2020-11-12 15:27 ` Serge Semin
2020-11-12 15:43 ` Miquel Raynal
2020-11-12 16:10 ` Serge Semin
2020-11-12 16:15 ` Miquel Raynal
2020-11-12 16:21 ` Serge Semin
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