Re: [PATCH 01/15] drm/i915: Add i915_gem_object_write() to i915_gem.c

Dave Gordon
2015-06-17T07:23:43Z

On 15/06/15 21:09, Chris Wilson wrote:
> On Mon, Jun 15, 2015 at 07:36:19PM +0100, Dave Gordon wrote:
>> From: Alex Dai <yu.dai@intel.com>
>>
>> i915_gem_object_write() is a generic function to copy data from a plain
>> linear buffer to a paged gem object.
>>
>> We will need this for the microcontroller firmware loading support code.
>>
>> Issue: VIZ-4884
>> Signed-off-by: Alex Dai <yu.dai@intel.com>
>> Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
>> ---
>> drivers/gpu/drm/i915/i915_drv.h | 2 ++
>> drivers/gpu/drm/i915/i915_gem.c | 28 ++++++++++++++++++++++++++++
>> 2 files changed, 30 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 611fbd8..9094c06 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -2713,6 +2713,8 @@ void *i915_gem_object_alloc(struct drm_device *dev);
>> void i915_gem_object_free(struct drm_i915_gem_object *obj);
>> void i915_gem_object_init(struct drm_i915_gem_object *obj,
>> const struct drm_i915_gem_object_ops *ops);
>> +int i915_gem_object_write(struct drm_i915_gem_object *obj,
>> + const void *data, size_t size);
>> struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
>> size_t size);
>> void i915_init_vm(struct drm_i915_private *dev_priv,
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>> index be35f04..75d63c2 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -5392,3 +5392,31 @@ bool i915_gem_obj_is_pinned(struct drm_i915_gem_object *obj)
>> return false;
>> }
>>
>> +/* Fill the @obj with the @size amount of @data */
>> +int i915_gem_object_write(struct drm_i915_gem_object *obj,
>> + const void *data, size_t size)
>> +{
>> + struct sg_table *sg;
>> + size_t bytes;
>> + int ret;
>> +
>> + ret = i915_gem_object_get_pages(obj);
>> + if (ret)
>> + return ret;
>> +
>> + i915_gem_object_pin_pages(obj);
>
> You don't set the object into the CPU domain, or instead manually handle
> the domain flushing. You don't handle objects that cannot be written
> directly by the CPU, nor do you handle objects whose representation in
> memory is not linear.
> -Chris

No we don't handle just any random gem object, but we do return an error
code for any types not supported. However, as we don't really need the
full generality of writing into a gem object of any type, I will replace
this function with one that combines the allocation of a new object
(which will therefore definitely be of the correct type, in the correct
domain, etc) and filling it with the data to be preserved.

Bikeshedding over the name of such function welcome :)

.Dave.