Re: [PATCH 05/10] uio_hv_generic: make ring size configurable

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On Tue, Jan 09, 2018 at 10:53:10AM -0800, Stephen Hemminger wrote:
> On Tue, 9 Jan 2018 19:42:40 +0100
> Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > On Thu, Jan 04, 2018 at 02:13:29PM -0800, Stephen Hemminger wrote:
> > > Allow setting size of ring buffer for host communication via
> > > module parameter.
> > > 
> > > Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> > > ---
> > >  drivers/uio/uio_hv_generic.c | 25 +++++++++++++++++++++----
> > >  1 file changed, 21 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
> > > index 8d5f529a1dc1..24f8689fdb14 100644
> > > --- a/drivers/uio/uio_hv_generic.c
> > > +++ b/drivers/uio/uio_hv_generic.c
> > > @@ -39,6 +39,13 @@
> > >  #define DRIVER_AUTHOR	"Stephen Hemminger <sthemmin at microsoft.com>"
> > >  #define DRIVER_DESC	"Generic UIO driver for VMBus devices"
> > >  
> > > +#define RING_SIZE_MIN 64
> > > +#define RING_SIZE_MAX 512
> > > +
> > > +static unsigned int ring_size = 128;
> > > +module_param(ring_size, uint, 0444);
> > > +MODULE_PARM_DESC(ring_size, "Ring buffer size (# of pages)");  
> > 
> > Ugh, really?  Module parameters suck rocks.  No other way to do this
> > dynamically?  This affects all devices for the driver, is that ok?
> > 
> > And how does anyone know to change this or not?  Why would it be
> > changed?  Why can't the kernel get this right on its own?
> 
> You made UIO API so restrictive there is no parameterization available.

_I_ did?  Heck, I don't remember what I did last month, let alone almost
a decade ago...

> The size of ring buffer is generally unchanged. 

Then why is this needed at all?

greg k-h
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