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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sun, 12 Jul 2020 17:34:15 +0200
Message-ID: <CAK8P3a2zr5JXr0K_vwJSkmH-YAbYbZtWFD8Pk-TOOdZhitw44A@mail.gmail.com>
Subject: Re: [PATCH 09/20] dlb2: add ioctl to configure ports, query poll mode
To:     Gage Eads <gage.eads@intel.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        gregkh <gregkh@linuxfoundation.org>, magnus.karlsson@intel.com,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>
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On Sun, Jul 12, 2020 at 3:46 PM Gage Eads <gage.eads@intel.com> wrote:
>  enum dlb2_user_interface_commands {
>         DLB2_CMD_GET_DEVICE_VERSION,
>         DLB2_CMD_CREATE_SCHED_DOMAIN,
>         DLB2_CMD_GET_SCHED_DOMAIN_FD,
>         DLB2_CMD_GET_NUM_RESOURCES,
>         DLB2_CMD_GET_DRIVER_VERSION,
> +       DLB2_CMD_QUERY_CQ_POLL_MODE,
>
>         /* NUM_DLB2_CMD must be last */
>         NUM_DLB2_CMD,

> @@ -427,6 +513,8 @@ struct dlb2_get_dir_queue_depth_args {
>  enum dlb2_domain_user_interface_commands {
>         DLB2_DOMAIN_CMD_CREATE_LDB_QUEUE,
>         DLB2_DOMAIN_CMD_CREATE_DIR_QUEUE,
> +       DLB2_DOMAIN_CMD_CREATE_LDB_PORT,
> +       DLB2_DOMAIN_CMD_CREATE_DIR_PORT,
>         DLB2_DOMAIN_CMD_GET_LDB_QUEUE_DEPTH,
>         DLB2_DOMAIN_CMD_GET_DIR_QUEUE_DEPTH,


You cannot add new commands in the middle without changing the ABI.

Maybe use individual #define lines in place of the enum to make sure these
remain constants, or add a numeric value for each one when they are
originally introduced.

(yes, I realize this is the initial contribution of the new driver, but it still
seems wrong to have it change in the middle of the series).

      Arnd