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To: Thomas Monjalon <thomas@monjalon.net>
Cc: dev@dpdk.org, Elena Agostini <eagostini@nvidia.com>,
 david.marchand@redhat.com
References: <20210602203531.2288645-1-thomas@monjalon.net>
 <38e4c145-e561-0707-a3b1-17a8f6cee75e@oktetlabs.ru>
 <2561723.R1Na977jkj@thomas>
From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Organization: OKTET Labs
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Date: Thu, 3 Jun 2021 10:49:41 +0300
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Subject: Re: [dpdk-dev] [PATCH] gpudev: introduce memory API
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On 6/3/21 10:26 AM, Thomas Monjalon wrote:
> 03/06/2021 09:06, Andrew Rybchenko:
>> On 6/2/21 11:35 PM, Thomas Monjalon wrote:
>>> + * Allocate a chunk of memory on the GPU.
>>
>> Looking a below function it is required to clarify here if
>> the memory is visible or invisible to GPU (or both allowed).
> 
> This function allocates on the GPU so it is visible by the GPU.
> I feel I misunderstand your question.

Below function says rte_gpu_malloc_visible() and its
description highlights that allocated memory is visible to GPU.
My problem that I don't understand what's the difference
between these two functions.

>>> + */
>>> +__rte_experimental
>>> +int rte_gpu_malloc(uint16_t gpu_id, size_t size, void **ptr);
>>
>> May be *malloc() should return a pointer and "negative"
>> values used to report various errnos?
> 
> I don't understand what you mean by negative values if it is a pointer.
> We could return a pointer and use rte_errno.

I was talking about something like (void *)(-ENOMEM), but it is
a bad idea. NULL + rte_errno is much better.

However, may be I'd kept callback as is set rte_error in lib if
negative value is returned by the callback. This way we'll be
safe against lost rte_errno update in drivers.