lkml.org 
[lkml]   [2015]   [Jul]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCHv3 08/16] staging: vme_user: provide DMA functionality
    On 07/07/15 13:51, Alessio Igor Bogani wrote:
    >> Current VME stack links windows not to the boards, but to device drivers.
    >> >Driver
    >> >could potentially minimise window usage within it’s scope (any sort of
    >> >window
    >> >reusing, like mapping whole A16 once to be used with all boards), but this
    >> >won’t
    >> >work across multiple drivers. Even if all of your drivers are window-wise
    >> >economic,
    >> >they will still need some amount of windows per each driver. Not that we
    >> >have that
    >> >many kernel drivers...
    > Yes you can share a window/image between all boards of the same type
    > (in effect we are porting our drivers in this way)*but* it isn't the
    > expected way to work (see Documentation/vme_api.txt struct
    > vme_driver's probe() and match() functions and the GE PIO2 VME
    > driver).

    I think it's perfectly valid to use a single window to dynamically map
    to the address space belonging to one of a number of devices supported
    by a single driver. I think this is almost preferable to mapping a large
    window over a large portion of the VME address space to drive a number
    of devices as (depending on there spacing in the VME address space) the
    latter could cause issues with filling available PCI address space.
    Admittedly this is more of a problem on 32-bit systems, but...

    --
    Martyn Welch (Lead Software Engineer) | Registered in England and Wales
    GE Intelligent Platforms | (3828642) at 100 Barbirolli Square
    T +44(0)1327322748 | Manchester, M2 3AB
    E martyn.welch@ge.com | VAT:GB 927559189


    \
     
     \ /
      Last update: 2015-07-08 16:01    [W:4.971 / U:0.032 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site