* 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 --]
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^ 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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