Re: [PATCH v5 3/3] media: i2c: imx471: Add Sony IMX471 image sensor driver

[Tarang Raval]

Hi Kieran,

> Quoting Kate Hsuan (2026-06-24 04:35:08)                                      
> > Add a new driver for Sony imx471 camera sensor. It is based on              
> > Jimmy Su <jimmy.su@xxxxxxxxx> implementation and the driver can be found    
> > in the following URL.                                                       
> > https://github.com/intel/ipu6-drivers/commits/master/drivers/media/i2c/imx471.c
> >                                                                             
> > This sensor can be found on Lenovo X1 Carbon G14, X9-14 and X9-15 laptops   
> > and it is a part of IPU7 solution. The driver was tested on Lenovo X1       
> > Carbon G14, X9-14 and X9-15 laptops.                                        
> >                                                                             
> > Signed-off-by: Kate Hsuan <hpa@xxxxxxxxxx>                                  
> > ---                                                                         
>                                                                               
> ... <snip>                                                                    
>                                                                               
> > +#define IMX471_REG_EXCK_FREQ                   CCI_REG16(0x0136)           
> > +#define IMX471_EXCK_FREQ(n)                    ((n) * 256)     /* n in MHz */
> >                                                                             
>                                                                               
> <snip>                                                                        
>                                                                               
> > +                                                                           
> > +static const struct cci_reg_sequence imx471_global_regs[] = {              
> > +       { IMX471_REG_EXCK_FREQ, IMX471_EXCK_FREQ(19.2) },                   
>                                                                               
>                                                                               
> Does this work? Is this a compile time constant multiplying floating          
> point with the compiler, or something happening in the kernel?                
>                                                                               
> I'll be happy if it does, but it catches my attention as something I          
> thought we couldn't do.                                                       
                                                                                
I tested this with GCC. It evaluates the expression at compile time and
folds it into the integer constant 4915. The generated assembly/object
file contains .quad 4915 in the initialized data and no floating-point 
instructions are emitted, so the kernel only ever sees the integer value.                                                                          
                                                                                
Best Regards,                                                                   
Tarang