Subject: Re: [PATCH net-next 3/5] r8152: add MCU typed read/write functions

From: Marek Behún <[email-masked]>
Date: Wed, 4 Nov 2020 12:10:53 +0100

On Wed, 4 Nov 2020 13:00:59 +0200
Vladimir Oltean <[email-masked]> wrote:

> On Wed, Nov 04, 2020 at 11:35:45AM +0100, Marek Behún wrote:
> > Or something like this?
> > 
> > #define DEF_R_FUNC(_t, _r, _r_i, _mcu)				\
> > static inline _t _r(struct r8152 *tp, u16 index)		\
> > {								\
> > 	return _r_i(tp, _mcu, index);				\
> > }
> > 
> > #define DEF_W_FUNC(_t, _w, _w_i, _mcu)				\
> > static inline void _w(struct r8152 *tp, u16 index, _t data)	\
> > {								\
> > 	_w_i(tp, _mcu, index, data);				\
> > }
> > 
> > DEF_R_FUNC(u8, pla_ocp_read_byte, ocp_read_byte, MCU_TYPE_PLA)
> > DEF_W_FUNC(u8, pla_ocp_write_byte, ocp_write_byte, MCU_TYPE_PLA)
> > DEF_R_FUNC(u16, pla_ocp_read_word, ocp_read_word, MCU_TYPE_PLA)
> > DEF_W_FUNC(u16, pla_ocp_write_word, ocp_write_word, MCU_TYPE_PLA)
> > DEF_R_FUNC(u32, pla_ocp_read_dword, ocp_read_dword, MCU_TYPE_PLA)
> > DEF_W_FUNC(u32, pla_ocp_write_dword, ocp_write_dword, MCU_TYPE_PLA)
> > 
> > DEF_R_FUNC(u8, usb_ocp_read_byte, ocp_read_byte, MCU_TYPE_USB)
> > DEF_W_FUNC(u8, usb_ocp_write_byte, ocp_write_byte, MCU_TYPE_USB)
> > DEF_R_FUNC(u16, usb_ocp_read_word, ocp_read_word, MCU_TYPE_USB)
> > DEF_W_FUNC(u16, usb_ocp_write_word, ocp_write_word, MCU_TYPE_USB)
> > DEF_R_FUNC(u32, usb_ocp_read_dword, ocp_read_dword, MCU_TYPE_USB)
> > DEF_W_FUNC(u32, usb_ocp_write_dword, ocp_write_dword, MCU_TYPE_USB)  
> 
> I'm not sure it's worth the change :(
> Let's put it another way, your diffstat has 338 insertions and 335
> deletions. Aka you're saving 3 lines overall.
> With this new approach that doesn't use token concatenation at all,
> you're probably not saving anything at all.
> Also, I'm not sure that you need to make the functions inline. The
> compiler should be smart enough to not generate functions for
> usb_ocp_read_byte etc. You can check with
> "make drivers/net/usb/r8152.lst".

Vladimir, the purpose of this patch isn't to save lines, but to save us
from always writing MCU_TYPE_USB / MCU_TYPE_PLA.
It just transforms forms of
  ocp_read_word(tp, MCU_TYPE_USB, idx);
  ocp_write_dword(tp, MCU_TYPE_PLA, idx, val);
into
  usb_ocp_read_word(tp, idx);
  pla_ocp_write_dword(tp, idx, val);

The fifth patch of this series saves lines by adding _modify functions,
to transform
  val = *_read(idx);
  val &= ~clr;
  val |= set;
  *_write(idx, val);
into
  *_modify(idx, clr, set);