Re: [PATCH v3 1/7] drm: add drm_print_bits

On Wed, 04 Sep 2019, Gerd Hoffmann kraxel@redhat.com wrote:

New helper to print named bits of some value (think flags fields).

Signed-off-by: Gerd Hoffmann kraxel@redhat.com

include/drm/drm_print.h | 3 +++ drivers/gpu/drm/drm_print.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+)

diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h index 112165d3195d..12d4916254b4 100644 --- a/include/drm/drm_print.h +++ b/include/drm/drm_print.h @@ -89,6 +89,9 @@ __printf(2, 3) void drm_printf(struct drm_printer *p, const char *f, ...); void drm_puts(struct drm_printer *p, const char *str); void drm_print_regset32(struct drm_printer *p, struct debugfs_regset32 *regset); +void drm_print_bits(struct drm_printer *p,

•     unsigned long value, const char *bits[],
  

•     unsigned int from, unsigned int to);
  
  

__printf(2, 0) /** diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c index ad302d71eeee..dfa27367ebb8 100644 --- a/drivers/gpu/drm/drm_print.c +++ b/drivers/gpu/drm/drm_print.c @@ -185,6 +185,39 @@ void drm_printf(struct drm_printer *p, const char *f, ...) } EXPORT_SYMBOL(drm_printf);

+/**

• • drm_print_bits - print bits to a &drm_printer stream
• • Print bits (in flag fields for example) in human readable form.
• • The first name in the @bits array is for the bit indexed by @from.
• • @p: the &drm_printer
• • @value: field value.
• • @bits: Array with bit names.
• • @from: start of bit range to print (inclusive).
• • @to: end of bit range to print (exclusive).
• */

+void drm_print_bits(struct drm_printer *p,

•     unsigned long value, const char *bits[],
  

•     unsigned int from, unsigned int to)
  

+{

• bool first = true;
• unsigned int i;
• for (i = from; i < to; i++) {

• if (!(value & (1 << i)))
  

• 	continue;
  

for_each_set_bit from bitops.h?

• if (WARN_ON_ONCE(!bits[i-from]))
  

• 	continue;
  

• drm_printf(p, "%s%s", first ? "" : ",",
  

• 	   bits[i-from]);
  

I wonder about the usefulness of from and to, as well as indexing (i-from) for the strings.

To limit the values to be printed in a more general way than range, you can use:

drm_print_bits(p, value & GENMASK(h, l), bits);

And obviously to adjust the starting position:

drm_print_bits(p, value >> l, bits);

Seems like a simple len parameter to indicate the ARRAY_SIZE() of bits would be more straighforward to guard against array overflow.

drm_print_bits(p, value, bits, ARRAY_SIZE(bits));

BR, Jani.

• first = false;
  

• }
• if (first)

• drm_printf(p, "(none)");
  

+} +EXPORT_SYMBOL(drm_print_bits);

void drm_dev_printk(const struct device *dev, const char *level, const char *format, ...) {