Messages in this thread | | | Date | Thu, 7 Jul 2022 11:03:49 -0700 | From | Nathan Chancellor <> | Subject | Re: [PATCH] eeprom: idt_89hpesx: fix clang -Wformat warnings |
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On Fri, Jul 01, 2022 at 04:20:31PM -0700, Justin Stitt wrote: > see warnings: > | drivers/misc/eeprom/idt_89hpesx.c:570:5: error: format specifies type > | 'unsigned char' but the argument has type 'u16' (aka 'unsigned short') > | [-Werror,-Wformat] memaddr); > - > | drivers/misc/eeprom/idt_89hpesx.c:579:5: error: format specifies type > | 'unsigned char' but the argument has type 'u16' (aka 'unsigned short') > | [-Werror,-Wformat] memaddr); > - > | drivers/misc/eeprom/idt_89hpesx.c:814:4: error: format specifies type > | 'unsigned short' but the argument has type 'unsigned int' > | [-Werror,-Wformat] CSR_REAL_ADDR(csraddr)); > > There's an ongoing movement to eventually enable the -Wformat flag for > clang. See: https://github.com/ClangBuiltLinux/linux/issues/378 > > The format specifier for idt_89hpesx.c:570 and 579 was `0x%02hhx`. The > part we care about `%hhx` describes a single byte format, wherein the > leftmost byte of our u16 type (of which memaddr is) is truncated. > > example: > ``` > uint16_t x = 0xbabe; > printf("%hhx\n", x); > // output is: be > // we lost 'ba' > ``` > > There exists a similar issue at idt_89hpesx.c:814 which involves the > CSR_REAL_ADDR macro. This macro returns a u16 but due to default > argument promotion for variadic functions (printf-like) actually > provides an int to the dev_err method. > > My proposed solution is to expand the width of the format specifier to > fully encompass the provided argument (which is promoted to an int, see > below). I opted for '%x' as this specifies an unsigned hexadecimal > integer which, with a guarantee, can represent all the values of a u16.
Additionally, this solution is in line with printk-formats.rst after commit cbacb5ab0aa0 ("docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]").
> As per C11 6.3.1.1: > (https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) > `If an int can represent all values of the original type ..., the > value is converted to an int; otherwise, it is converted to an > unsigned int. These are called the integer promotions.` > > Link: https://github.com/ClangBuiltLinux/linux/issues/378 > Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> --- > drivers/misc/eeprom/idt_89hpesx.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/misc/eeprom/idt_89hpesx.c b/drivers/misc/eeprom/idt_89hpesx.c > index b0cff4b152da..42eac114edd7 100644 > --- a/drivers/misc/eeprom/idt_89hpesx.c > +++ b/drivers/misc/eeprom/idt_89hpesx.c > @@ -566,7 +566,7 @@ static int idt_eeprom_read_byte(struct idt_89hpesx_dev *pdev, u16 memaddr, > eeseq.memaddr = cpu_to_le16(memaddr); > ret = pdev->smb_write(pdev, &smbseq); > if (ret != 0) { > - dev_err(dev, "Failed to init eeprom addr 0x%02hhx", > + dev_err(dev, "Failed to init eeprom addr 0x%02x", > memaddr); > break; > } > @@ -575,7 +575,7 @@ static int idt_eeprom_read_byte(struct idt_89hpesx_dev *pdev, u16 memaddr, > smbseq.bytecnt = EEPROM_RD_CNT; > ret = pdev->smb_read(pdev, &smbseq); > if (ret != 0) { > - dev_err(dev, "Failed to read eeprom data 0x%02hhx", > + dev_err(dev, "Failed to read eeprom data 0x%02x", > memaddr); > break; > } > @@ -810,7 +810,7 @@ static int idt_csr_read(struct idt_89hpesx_dev *pdev, u16 csraddr, u32 *data) > smbseq.bytecnt = CSR_RD_CNT; > ret = pdev->smb_read(pdev, &smbseq); > if (ret != 0) { > - dev_err(dev, "Failed to read csr 0x%04hx", > + dev_err(dev, "Failed to read csr 0x%04x", > CSR_REAL_ADDR(csraddr)); > goto err_mutex_unlock; > } > -- > 2.37.0.rc0.161.g10f37bed90-goog >
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