On Thu, 2015-09-17 at 15:19 -0500, Scott Wood wrote:

On Mon, 2015-09-14 at 09:38 +0800, Zhao Qiang wrote:

quoted

Add new algo for genalloc, it reserve a specific region of
memory matching the size requirement (no alignment constraint)

Signed-off-by: Zhao Qiang <redacted>
---
Changes for v9:
      - reserve a specific region, if the return region
      - is not during the specific region, return fail.

 include/linux/genalloc.h | 11 +++++++++++
 lib/genalloc.c           | 30 ++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
index aaf3dc2..85e3b2f 100644
--- a/include/linux/genalloc.h
+++ b/include/linux/genalloc.h

@@ -82,6 +82,13 @@ struct genpool_data_align {
      int align;              /* alignment by bytes for starting address 

*/
 };
 
+/*
+ *  gen_pool data descriptor for gen_pool_fixed_fit.
+ */
+struct genpool_data_fixed {
+     unsigned long offset;           /* The offset of the specific 
region */
+};
+
 extern struct gen_pool *gen_pool_create(int, int);
 extern phys_addr_t gen_pool_virt_to_phys(struct gen_pool *pool, unsigned 
long);
 extern int gen_pool_add_virt(struct gen_pool *, unsigned long, 
phys_addr_t,

@@ -121,6 +128,10 @@ extern unsigned long gen_pool_first_fit(unsigned 

long 
*map, unsigned long size,
              unsigned long start, unsigned int nr, void *data,
              struct gen_pool *pool);
 
+extern unsigned long gen_pool_fixed_fit(unsigned long *map,
+             unsigned long size, unsigned long start, unsigned int nr,
+             void *data, struct gen_pool *pool);
+

"fixed fit" doesn't make much sense...  How about "fixed_alloc"?

 /**

quoted

+ * gen_pool_fixed_fit - reserve a specific region of
+ * matching the size requirement (no alignment constraint)
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @data: data for alignment
+ * @pool: pool to get order from
+ */
+unsigned long gen_pool_fixed_fit(unsigned long *map, unsigned long size,
+             unsigned long start, unsigned int nr, void *data,
+             struct gen_pool *pool)
+{
+     struct genpool_data_fixed *fixed_data;
+     int order;
+     unsigned long offset_bit;
+     unsigned long start_bit;
+
+     fixed_data = data;
+     order = pool->min_alloc_order;
+     offset_bit = fixed_data->offset >> order;
+     start_bit = bitmap_find_next_zero_area(map, size,
+                     start + offset_bit, nr, 0);
+     if (start_bit != offset_bit)
+             start_bit = size;
+     return start_bit;
+}
+EXPORT_SYMBOL(gen_pool_fixed_fit);

This would be simpler with bitmap_allocate_region().

Never mind, that doesn't fit with how the algorithm is used by the caller, 
and unlike genalloc isn't atomic.

-Scott