[dpdk-dev] [PATCH v3 00/15] Introduce SoC device/driver framework for EAL

[Jianbo Liu]

On 9 September 2016 at 16:43, Shreyansh Jain <shreyansh.jain at nxp.com> wrote:
> Introduction:
> =============
>
> This patch set is direct derivative of Jan's original series [1],[2].
>
>  - As this deviates substantially from original series, if need be I can
>    post it as a separate patch rather than v2. Please suggest.
>  - Also, there are comments on original v1 ([4]) which are _not_
>    incorporated in this series as they refer to section no more in new
>    version.
>  - This v3 version is based on the rte_driver/device patchset v9 [10].
>    That series introduced device structures (rte_driver/rte_device)
>    generalizing devices into PCI, VDEV, XXX. For the purpose of this
>    patchset, XXX=>SOC.
>
> Aim:
> ====
>
> As of now EAL is primarly focused on PCI initialization/probing.
>
>  rte_eal_init()
>   |- rte_eal_pci_init(): Find PCI devices from sysfs
>   |- ...
>   |- rte_eal_memzone_init()
>   |- ...
>   `- rte_eal_pci_probe(): Driver<=>Device initialization
>
> This patchset introduces SoC framework which would enable SoC drivers and
> drivers to be plugged into EAL, very similar to how PCI drivers/devices are
> done today.
>
> This is a stripped down version of PCI framework which allows the SoC PMDs
> to implement their own routines for detecting devices and linking devices to
> drivers.
>
> 1) Changes to EAL
>  rte_eal_init()
>   |- rte_eal_pci_init(): Find PCI devices from sysfs
>   |- rte_eal_soc_init(): Calls PMDs->scan_fn
>   |- ...
>   |- rte_eal_memzone_init()
>   |- ...
>   |- rte_eal_pci_probe(): Driver<=>Device initialization, PMD->devinit()
>   `- rte_eal_soc_probe(): Calls PMDs->match_fn and PMDs->devinit();
>
> 2) New device/driver structures:
>   - rte_soc_driver (inheriting rte_driver)
>   - rte_soc_device (inheriting rte_device)
>   - rte_eth_dev and eth_driver embedded rte_soc_device and rte_soc_driver,
>     respectively.
>
> 3) The SoC PMDs need to:
>  - define rte_soc_driver with necessary scan and match callbacks
>  - Register themselves using DRIVER_REGISTER_SOC()
>  - Implement respective bus scanning in the scan callbacks to add necessary
>    devices to SoC device list
>  - Implement necessary eth_dev_init/uninint for ethernet instances
>
> 4) Design considerations that are same as PCI:
>  - SoC initialization is being done through rte_eal_init(), just after PCI
>    initialization is done.
>  - As in case of PCI, probe is done after rte_eal_pci_probe() to link the
>    devices detected with the drivers registered.
>  - Device attach/detach functions are available and have been designed on
>    the lines of PCI framework.
>  - PMDs register using DRIVER_REGISTER_SOC, very similar to
>    DRIVER_REGISTER_PCI for PCI devices.
>  - Linked list of SoC driver and devices exists independent of the other
>    driver/device list, but inheriting rte_driver/rte_driver, these are also
>    part of a global list.
>
> 5) Design considerations that are different from PCI:
>  - Each driver implements its own scan and match function. PCI uses the BDF
>    format to read the device from sysfs, but this _may_not_ be a case for a
>    SoC ethernet device.
>    = This is an important change from initial proposal by Jan in [2]. Unlike
>    his attempt to use /sys/bus/platform, this patch relies on the PMD to

It could be many redundant code if Each PMD driver has the scan
function if its own.
I think Jan's implementation is common to many platform drivers.

>    detect the devices. This is because SoC may require specific or
>    additional info for device detection. Further, SoC may have embedded

Can you give us more precise definition about SoC driver? Does it
include the driver in ARM server?

>    devices/MACs which require initialization which cannot be covered through
>    sysfs parsing.

I think it can be done in devinit, not in scan function. devinit can
be different for each driver.

>    = PCI based PMDs rely on EAL's capability to detect devices. This
>    proposal puts the onus on PMD to detect devices, add to soc_device_list
>    and wait for Probe. Matching, of device<=>driver is again PMD's callback.
>