[Intel-xe] [RFC 1/5] drm/netlink: Add netlink infrastructure

[Iddamsetty, Aravind]

On 04-06-2023 22:37, Tomer Tayar wrote:
> On 26/05/2023 19:20, Aravind Iddamsetty wrote:
>> Define the netlink commands and attributes that can be commonly used
>> across by drm drivers.
>>
>> Signed-off-by: Aravind Iddamsetty <aravind.iddamsetty at intel.com>
>> ---
>>   include/uapi/drm/drm_netlink.h | 68 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 68 insertions(+)
>>   create mode 100644 include/uapi/drm/drm_netlink.h
>>
>> diff --git a/include/uapi/drm/drm_netlink.h b/include/uapi/drm/drm_netlink.h
>> new file mode 100644
>> index 000000000000..28e7a334d0c7
>> --- /dev/null
>> +++ b/include/uapi/drm/drm_netlink.h
>> @@ -0,0 +1,68 @@
>> +/*
>> + * Copyright 2023 Intel Corporation
>> + *
>> + * Permission is hereby granted, free of charge, to any person obtaining a
>> + * copy of this software and associated documentation files (the "Software"),
>> + * to deal in the Software without restriction, including without limitation
>> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
>> + * and/or sell copies of the Software, and to permit persons to whom the
>> + * Software is furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice (including the next
>> + * paragraph) shall be included in all copies or substantial portions of the
>> + * Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
>> + * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
>> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
>> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
>> + * OTHER DEALINGS IN THE SOFTWARE.
>> + */
>> +
>> +#ifndef _DRM_NETLINK_H_
>> +#define _DRM_NETLINK_H_
>> +
>> +#include <linux/netdevice.h>
>> +#include <net/genetlink.h>
>> +#include <net/sock.h>
> 
> This is a uapi header.
> Are all header files here available for user?

no they are not, I later came to know that we should not have any of
that user can't use so will split the header into 2.
> Also, should we add here "#if defined(__cplusplus) extern "C" { ..."?

ya will add that
> 
>> +
>> +#define DRM_GENL_VERSION 1
>> +
>> +enum error_cmds {
>> +	DRM_CMD_UNSPEC,
>> +	/* command to list all errors names with config-id */
>> +	DRM_CMD_QUERY,
>> +	/* command to get a counter for a specific error */
>> +	DRM_CMD_READ_ONE,
>> +	/* command to get counters of all errors */
>> +	DRM_CMD_READ_ALL,
>> +
>> +	__DRM_CMD_MAX,
>> +	DRM_CMD_MAX = __DRM_CMD_MAX - 1,
>> +};
>> +
>> +enum error_attr {
>> +	DRM_ATTR_UNSPEC,
>> +	DRM_ATTR_PAD = DRM_ATTR_UNSPEC,
>> +	DRM_ATTR_REQUEST, /* NLA_U8 */
>> +	DRM_ATTR_QUERY_REPLY, /*NLA_NESTED*/
> 
> Missing spaces in /*NLA_NESTED*/
> 
>> +	DRM_ATTR_ERROR_NAME, /* NLA_NUL_STRING */
>> +	DRM_ATTR_ERROR_ID, /* NLA_U64 */
>> +	DRM_ATTR_ERROR_VALUE, /* NLA_U64 */
>> +
>> +	__DRM_ATTR_MAX,
>> +	DRM_ATTR_MAX = __DRM_ATTR_MAX - 1,
>> +};
>> +
>> +/* attribute policies */
>> +static const struct nla_policy drm_attr_policy_query[DRM_ATTR_MAX + 1] = {
>> +	[DRM_ATTR_REQUEST] = { .type = NLA_U8 },
>> +};
> 
> Should these policies structures be in uapi?

so ya these will also likely move into a separate drm header as
userspace would define there own policy.
> 
>> +
>> +static const struct nla_policy drm_attr_policy_read_one[DRM_ATTR_MAX + 1] = {
>> +	[DRM_ATTR_ERROR_ID] = { .type = NLA_U64 },
>> +};
> 
> I might miss something here, but why it is not a single policy structure 
> with entries for DRM_ATTR_REQUEST and DRM_ATTR_ERROR_ID?

so each command can have it's own policy defined, i.e what attributes it
expects we could define only those, that way we can have a check as
well. So, in the present implementation DRM_CMD_QUERY and
DRM_CMD_READ_ALL expect only DRM_ATTR_REQUEST and while DRM_CMD_READ_ONE
expects only DRM_ATTR_ERROR_ID as part of the incoming message from user.

Thanks,
Aravind.
> 
> Thanks,
> Tomer
> 
>> +
>> +#endif
> 
>