Messages in this thread | | | Date | Thu, 15 Feb 2018 20:25:36 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH v14 3/9] fw_cfg: fix sparse warnings in fw_cfg_sel_endianness() |
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On Thu, Feb 15, 2018 at 10:34:28AM +0100, Marc-Andre Lureau wrote: > On Wed, Feb 14, 2018 at 9:46 PM, Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Feb 14, 2018 at 03:18:44PM +0100, Marc-André Lureau wrote: > >> The function is used for both LE & BE target type, use __force casting. > >> > >> Fixes: > >> $ make C=1 CF=-D__CHECK_ENDIAN__ drivers/firmware/qemu_fw_cfg.o > >> > >> drivers/firmware/qemu_fw_cfg.c:55:33: warning: restricted __be16 degrades to integer > >> drivers/firmware/qemu_fw_cfg.c:55:52: warning: restricted __le16 degrades to integer > >> > >> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> > >> --- > >> drivers/firmware/qemu_fw_cfg.c | 4 +++- > >> 1 file changed, 3 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c > >> index 90f467232777..85e693287d87 100644 > >> --- a/drivers/firmware/qemu_fw_cfg.c > >> +++ b/drivers/firmware/qemu_fw_cfg.c > >> @@ -52,7 +52,9 @@ static DEFINE_MUTEX(fw_cfg_dev_lock); > >> /* pick appropriate endianness for selector key */ > >> static inline u16 fw_cfg_sel_endianness(u16 key) > >> { > >> - return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key); > >> + return fw_cfg_is_mmio ? > >> + (u16 __force)cpu_to_be16(key) : > >> + (u16 __force)cpu_to_le16(key); > >> } > >> > >> /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */ > > > > Well the caller does cpu_to_le16 on the result ... > > All this makes my head spin. > > > > IMHO what you want is a wrapper that does iowrite and iowritebe > > rather than __force. > > iowrite16(key) is the same as iowrite16(cpu_to_le16(key)) ? There is > no iowrite16le()...
Yes.
> Is this equivalent, and not introducing regressions? > > static inline u16 fw_cfg_sel_endianness(u16 key) > +static void fw_cfg_sel_endianness(u16 key) > { > - return fw_cfg_is_mmio ? cpu_to_be16(key) : cpu_to_le16(key);
For mmio on LE it does 1 swap. On BE 1 swap. For non mmio on LE it does no swaps. On BE 1 swap.
Fair summary?
And is this actually the intended behaviour.
> + if (fw_cfg_is_mmio) > + iowrite16be(key, fw_cfg_reg_ctrl); > + else > + iowrite16(key, fw_cfg_reg_ctrl);
this behaves differently. donnu if that's a bug or a feature. You will have to find out.
> } > > /* read chunk of given fw_cfg blob (caller responsible for sanity-check) */ > @@ -74,7 +77,7 @@ static inline void fw_cfg_read_blob(u16 key, > } > > mutex_lock(&fw_cfg_dev_lock); > - iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl); > + fw_cfg_sel_endianness(key); > > > > > > >> -- > >> 2.16.1.73.g5832b7e9f2
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