lkml.org 
[lkml]   [2019]   [May]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [alsa-devel] [RFC PATCH 1/7] soundwire: Add sysfs support for master(s)
    On Wed, May 08, 2019 at 11:42:15AM -0500, Pierre-Louis Bossart wrote:
    >
    >
    > On 5/8/19 4:16 AM, Greg KH wrote:
    > > On Wed, May 08, 2019 at 01:16:06PM +0530, Vinod Koul wrote:
    > > > On 07-05-19, 17:49, Pierre-Louis Bossart wrote:
    > > > >
    > > > > > > The model here is that Master device is PCI or Platform device and then
    > > > > > > creates a bus instance which has soundwire slave devices.
    > > > > > >
    > > > > > > So for any attribute on Master device (which has properties as well and
    > > > > > > representation in sysfs), device specfic struct (PCI/platfrom doesn't
    > > > > > > help). For slave that is not a problem as sdw_slave structure takes care
    > > > > > > if that.
    > > > > > >
    > > > > > > So, the solution was to create the psedo sdw_master device for the
    > > > > > > representation and have device-specific structure.
    > > > > >
    > > > > > Ok, much like the "USB host controller" type device. That's fine, make
    > > > > > such a device, add it to your bus, and set the type correctly. And keep
    > > > > > a pointer to that structure in your device-specific structure if you
    > > > > > really need to get to anything in it.
    > > > >
    > > > > humm, you lost me on the last sentence. Did you mean using
    > > > > set_drv/platform_data during the init and retrieving the bus information
    > > > > with get_drv/platform_data as needed later? Or something else I badly need
    > > > > to learn?
    > > >
    > > > IIUC Greg meant we should represent a soundwire master device type and
    > > > use that here. Just like we have soundwire slave device type. Something
    > > > like:
    > > >
    > > > struct sdw_master {
    > > > struct device dev;
    > > > struct sdw_master_prop *prop;
    > > > ...
    > > > };
    > > >
    > > > In show function you get master from dev (container of) and then use
    > > > that to access the master properties. So int.sdw.0 can be of this type.
    > >
    > > Yes, you need to represent the master device type if you are going to be
    > > having an internal representation of it.
    >
    > Humm, confused...In the existing code bus and master are synonyms, see e.g.
    > following code excerpts:
    >
    > * sdw_add_bus_master() - add a bus Master instance
    > * @bus: bus instance
    > *
    > * Initializes the bus instance, read properties and create child
    > * devices.
    >
    > struct sdw_bus {
    > struct device *dev; <<< pointer here

    That's the pointer to what? The device that the bus is "attached to"
    (i.e. parent, like a platform device or a pci device)?

    Why isn't this a "real" device in itself?

    I thought I asked that a long time ago when first reviewing these
    patches...

    > unsigned int link_id;
    > struct list_head slaves;
    > DECLARE_BITMAP(assigned, SDW_MAX_DEVICES);
    > struct mutex bus_lock;
    > struct mutex msg_lock;
    > const struct sdw_master_ops *ops;
    > const struct sdw_master_port_ops *port_ops;
    > struct sdw_bus_params params;
    > struct sdw_master_prop prop;
    >
    > The existing code creates a platform_device in
    > drivers/soundwire/intel_init.c, and it's assigned by the following code:

    The core creates a platform device, don't assume you can "take it over"
    :)

    That platform device lives on the platform bus, you need a "master"
    device that lives on your soundbus bus.

    Again, look at how USB does this. Or better yet, greybus, as that code
    is a lot smaller and simpler.

    >
    > static int intel_probe(struct platform_device *pdev)
    > {
    > struct sdw_cdns_stream_config config;
    > struct sdw_intel *sdw;
    > int ret;
    >
    > sdw = devm_kzalloc(&pdev->dev, sizeof(*sdw), GFP_KERNEL);
    > [snip]
    > sdw->cdns.dev = &pdev->dev;
    > sdw->cdns.bus.dev = &pdev->dev;

    Gotta love the lack of reference counting :(

    > I really don't see what you are hinting at, sorry, unless we are talking
    > about major surgery in the code.

    It sounds like you need a device on your bus that represents the master,
    as you have attributes associated with it, and other things. You can't
    put attributes on a random pci or platform device, as you do not "own"
    that device.

    does that help?

    greg k-h

    \
     
     \ /
      Last update: 2019-05-08 21:53    [W:7.365 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site