linux-kernel - Re: [PATCH v10 1/2] lib/bitmap: add bitmap

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Date:   Thu, 26 Oct 2023 16:48:46 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     catalin.marinas@....com, will@...nel.org, pcc@...gle.com,
        andreyknvl@...il.com, aleksander.lobakin@...el.com,
        linux@...musvillemoes.dk, yury.norov@...il.com,
        alexandru.elisei@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, eugenis@...gle.com,
        syednwaris@...il.com, william.gray@...aro.org,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v10 1/2] lib/bitmap: add bitmap_{read,write}()

>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Thanks!

> One nit below, though.
>
> ...
>
> > +/**
> > + * bitmap_write - write n-bit value within a memory region
> > + * @map: address to the bitmap memory region
> > + * @value: value to write, clamped to nbits
> > + * @start: bit offset of the n-bit value
> > + * @nbits: size of value in bits, nonzero, up to BITS_PER_LONG.
> > + *
> > + * bitmap_write() behaves as-if implemented as @nbits calls of __assign_bit(),
> > + * i.e. bits beyond @nbits are ignored:
> > + *
> > + *   for (bit = 0; bit < nbits; bit++)
> > + *           __assign_bit(start + bit, bitmap, val & BIT(bit));
> > + *
> > + * For @nbits > BITS_PER_LONG no writes are performed.
>
> nbits == 0 hasn't been mentioned.

I can mention it explicitly, but it is already covered by the for-loop
above: if nbits==0, no bits are assigned.

>
> (no, the main nit below)
>
> > + */
> > +static inline void bitmap_write(unsigned long *map,
> > +                             unsigned long value,
> > +                             unsigned long start, unsigned long nbits)
>
> While noticing strange indentation (you have space for the parameter on
> the previous line,

I believe I do not, maybe that's something on your side?
There are tabs in the source, and in the original email.

> I realized that this is a counter-intuitive interface.
> Can you actually make value the last parameter?

It is consistent with bitmap_set_value8(map, value, start), and in all
the functions above @nbits is the last parameter.