Hi Julia, On Sat, Jul 01, 2017 at 09:28:10PM +0200, Julia Lawall wrote: > As reported by Sebastian Reichel, i2c_smbus_read_word_data() returns native > endianness for little-endian bus (it basically has builtin > le16_to_cpu). Calling le16_to_cpu on the result breaks support on big > endian machines by converting it back. Thanks, you are fast :) > This semantic patch give no reports on kernel code currently, but the > issue is somewhat obscure and has occurred in a sumitted patch, so it could > be good to have a check for it. Ok, so problem is not as bad as I feared. I found a few issues with simple git grep, though: git grep -C100 i2c_smbus_read_word_data | grep le16_to_cpu git grep -C100 i2c_smbus_write_word_data | grep cpu_to_le16 It returned just a few files on v4.12 and all of them look buggy after manual inspection: * drivers/macintosh/windfarm_lm75_sensor.c (line 71) * drivers/macintosh/windfarm_smu_sat.c (line 80-91) * drivers/gpio/gpio-pca953x.c (line 190-192) * drivers/power/supply/bq24735-charger.c - fixed in linux-next by 48f680c0a9ca * drivers/power/supply/sbs-battery.c - fixed in linux-next by a1bbec72f9fe > Suggested-by: Sebastian Reichel <sre@xxxxxxxxxx> > Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxx> > > --- > > The rule could easily be extended with more such functions. Let me know if > anything else should be taken into account. I guess the write function should also be covered. -- Sebastian > scripts/coccinelle/api/smbus_word.cocci | 45 ++++++++++++++++++++++++++++++++ > 1 file changed, 45 insertions(+) > > diff --git a/scripts/coccinelle/api/smbus_word.cocci b/scripts/coccinelle/api/smbus_word.cocci > new file mode 100644 > index 0000000..b167cf0 > --- /dev/null > +++ b/scripts/coccinelle/api/smbus_word.cocci > @@ -0,0 +1,45 @@ > +/// i2c_smbus_read_word_data() returns native endianness for little-endian > +/// bus (it basically has builtin le16_to_cpu). Calling le16_to_cpu on the > +/// result breaks support on big endian machines by converting it back. > +/// > +// Confidence: Moderate > +// Copyright: (C) 2017 Julia Lawall, Inria. GPLv2. > +// URL: http://coccinelle.lip6.fr/ > +// Options: --no-includes --include-headers > +// Keywords: i2c_smbus_read_word_data, le16_to_cpu > + > +virtual context > +virtual org > +virtual report > + > +// ---------------------------------------------------------------------------- > + > +@r depends on context || org || report exists@ > +expression e, x; > +position j0, j1; > +@@ > + > +* x@j0 = i2c_smbus_read_word_data(...) > +... when != x = e > +* le16_to_cpu@j1(x) > + > +// ---------------------------------------------------------------------------- > + > +@script:python r_org depends on org@ > +j0 << r.j0; > +j1 << r.j1; > +@@ > + > +msg = "le16_to_cpu not needed on i2c_smbus_read_word_data result." > +coccilib.org.print_todo(j0[0], msg) > +coccilib.org.print_link(j1[0], "") > + > +// ---------------------------------------------------------------------------- > + > +@script:python r_report depends on report@ > +j0 << r.j0; > +j1 << r.j1; > +@@ > + > +msg = "le16_to_cpu not needed on i2c_smbus_read_word_data result around line %s." % (j1[0].line) > +coccilib.report.print_report(j0[0], msg) >
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