Re: [PATCH v7 05/10] ACPI: property: Prepare generating swnodes for ACPI and DisCo for Imaging

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Hi Andy,

On Tue, Mar 28, 2023 at 06:44:40PM +0300, Andy Shevchenko wrote:
> On Tue, Mar 28, 2023 at 01:12:58PM +0300, Sakari Ailus wrote:
> > Prepare generating software nodes for information parsed from ACPI _CRS for
> > CSI-2 as well as MIPI DisCo for Imaging spec. The software nodes are
> > compliant with existing ACPI or DT definitions and are parsed by relevant
> > drivers without changes.
> 
> ...
> 
> >  #define NO_CSI2_PORT (UINT_MAX - 1)
> 
> Has it been used before this patch?

I don't think so.

It has its current form as you preferred it earlier. :-)

> 
> ...
> 
> > +/* Print graph port name into a buffer, return non-zero if failed. */
> > +#define GRAPH_PORT_NAME(var, num)					    \
> > +	(snprintf((var), sizeof(var), SWNODE_GRAPH_PORT_NAME_FMT, (num)) >= \
> > +	 sizeof(var))
> 
> This macro evaluates sizeof(var) twice. Is it a problem?

I don't think it is.

> 
> ...
> 
> > +#define NEXT_PROPERTY(index, max)				\
> > +	(WARN_ON(++(index) > ACPI_DEVICE_SWNODE_##max + 1) ?	\
> > +	 ACPI_DEVICE_SWNODE_##max : (index) - 1)
> 
> This macro full of interesting effects. On top of that it's written in
> hard-to-read form.
> 
> Why not at least
> 
> #define NEXT_PROPERTY(index, max)				\
> 	(WARN_ON((index) > ACPI_DEVICE_SWNODE_##max) ?	\
> 	 ACPI_DEVICE_SWNODE_##max : (index)++)
> 
> ?

This appears functionally (almost) equivalent --- it wouldn't overflow.
I'll use this in v8.

> 
> ...
> 
> > +	ret = fwnode_property_count_u8(mipi_port_fwnode, "mipi-img-lane-polarities");
> > +	if (ret > 0) {
> > +		unsigned int bytes = min_t(unsigned int, ret, sizeof(val));
> > +
> > +		fwnode_property_read_u8_array(mipi_port_fwnode,
> > +					      "mipi-img-lane-polarities",
> > +					      val, bytes);
> > +
> > +		/* Total number of lanes here is clock lane + data lanes */
> > +		if (bytes * BITS_PER_TYPE(u8) >= 1 + num_lanes) {
> > +			unsigned int i;
> > +
> > +			/* Move polarity bits to the lane polarity u32 array */
> > +			for (i = 0; i < 1 + num_lanes; i++)
> > +				port->lane_polarities[i] =
> > +					(bool)(val[i >> 3] & (1 << (i & 7)));
> 
> Casting to bool?!

This was the result of our earlier discussion on an earlier version of this
set.

> 
> Can we read the array and convert it to bitmap, then this voodoo-ish code can
> be simplified to
> 
> 	for_each_set_bit(i, ...)
> 		..._polarities[i] = 1;

for_each_set_bit() operates on unsigned longs (usually u32 or u64) but we
have u8s here. There's an endianness issue there.

> 
> (assuming initially they are 0:s)?

-- 
Kind regards,

Sakari Ailus



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