[Intel-gfx] [PATCH 03/19] drm/i915/gt: Add helper for shmem copy to dma_buf_map

[Lucas De Marchi]

Add a variant of shmem_read() that takes a dma_buf_map pointer rather
than a plain pointer as argument. It's mostly a copy __shmem_rw() but
adapting the api and removing the write support since there's currently
only need to use dma_buf_map as destination.

Reworking __shmem_rw() to share the implementation was tempting, but
finding a good balance between reuse and clarity pushed towards a little
code duplication. Since the function is small, just add the similar
function with a copy/paste/adapt approach.

Cc: Matt Roper <matthew.d.ro...@intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursu...@linux.intel.com>
Cc: David Airlie <airl...@linux.ie>
Cc: Daniel Vetter <dan...@ffwll.ch>
Cc: Matthew Auld <matthew.a...@intel.com>
Cc: Thomas Hellström <thomas.hellst...@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Signed-off-by: Lucas De Marchi <lucas.demar...@intel.com>
---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 32 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/gt/shmem_utils.h |  3 +++
 2 files changed, 35 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c 
b/drivers/gpu/drm/i915/gt/shmem_utils.c
index 0683b27a3890..d7968e68ccfb 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -3,6 +3,7 @@
  * Copyright © 2020 Intel Corporation
  */
 
+#include <linux/dma-buf-map.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/shmem_fs.h>
@@ -123,6 +124,37 @@ static int __shmem_rw(struct file *file, loff_t off,
        return 0;
 }
 
+int shmem_read_to_dma_buf_map(struct file *file, loff_t off,
+                             struct dma_buf_map *map, size_t len)
+{
+       struct dma_buf_map map_iter = *map;
+       unsigned long pfn;
+
+       for (pfn = off >> PAGE_SHIFT; len; pfn++) {
+               unsigned int this =
+                       min_t(size_t, PAGE_SIZE - offset_in_page(off), len);
+               struct page *page;
+               void *vaddr;
+
+               page = shmem_read_mapping_page_gfp(file->f_mapping, pfn,
+                                                  GFP_KERNEL);
+               if (IS_ERR(page))
+                       return PTR_ERR(page);
+
+               vaddr = kmap(page);
+               dma_buf_map_memcpy_to(&map_iter, vaddr + offset_in_page(off), 
this);
+               mark_page_accessed(page);
+               kunmap(page);
+               put_page(page);
+
+               len -= this;
+               dma_buf_map_incr(&map_iter, this);
+               off = 0;
+       }
+
+       return 0;
+}
+
 int shmem_read(struct file *file, loff_t off, void *dst, size_t len)
 {
        return __shmem_rw(file, off, dst, len, false);
diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.h 
b/drivers/gpu/drm/i915/gt/shmem_utils.h
index c1669170c351..a3d4ce966f74 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.h
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.h
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 
+struct dma_buf_map;
 struct drm_i915_gem_object;
 struct file;
 
@@ -17,6 +18,8 @@ struct file *shmem_create_from_object(struct 
drm_i915_gem_object *obj);
 void *shmem_pin_map(struct file *file);
 void shmem_unpin_map(struct file *file, void *ptr);
 
+int shmem_read_to_dma_buf_map(struct file *file, loff_t off,
+                             struct dma_buf_map *map, size_t len);
 int shmem_read(struct file *file, loff_t off, void *dst, size_t len);
 int shmem_write(struct file *file, loff_t off, void *src, size_t len);
 
-- 
2.35.0