Simple Read operation on a misc device driver

Simple Read operation on a misc device driver

[Aldo Esteban Paz]

For the Eudyptula's Chanllenge Task 6, i need to write a misc device
driver with simple read/write operations.
 The following was the answer to part of my code:

> static char eid[] = EUDYPTULAID;
>
> static ssize_t misc_device_read(struct file *file, char __user *buf,
>                                         size_t count, loff_t *ppos)
> {
>         if (*ppos == sizeof(eid))
>                 return 0;
>         else
>                 if (*ppos != 0 || count < sizeof(eid))
>                         return -EINVAL;
>
>         if (copy_to_user(buf, eid, sizeof(eid)))
>                 return -EINVAL;
>
>         *ppos = sizeof(eid);
>
>         return *ppos;
> }

This whole function can be made much more "simple" and reduced to one
single line {hint} (It's just a "simple" function call {hint}).

Anyone know that "single" function?

Simple Read operation on a misc device driver

[Greg KH]

On Fri, Apr 18, 2014 at 06:30:44PM -0300, Aldo Esteban Paz wrote:
> For the Eudyptula's Chanllenge Task 6, i need to write a misc device
> driver with simple read/write operations.
>  The following was the answer to part of my code:
> 
> > static char eid[] = EUDYPTULAID;
> >
> > static ssize_t misc_device_read(struct file *file, char __user *buf,
> >                                         size_t count, loff_t *ppos)
> > {
> >         if (*ppos == sizeof(eid))
> >                 return 0;
> >         else
> >                 if (*ppos != 0 || count < sizeof(eid))
> >                         return -EINVAL;
> >
> >         if (copy_to_user(buf, eid, sizeof(eid)))
> >                 return -EINVAL;
> >
> >         *ppos = sizeof(eid);
> >
> >         return *ppos;
> > }
> 
> This whole function can be made much more "simple" and reduced to one
> single line {hint} (It's just a "simple" function call {hint}).
> 
> Anyone know that "single" function?

Yes, but you really should do your own research for stuff like this,
that's what the challenge is all about, not asking others to do it for
you :(

Simple Read operation on a misc device driver

[L. Alberto Giménez]

On Fri, Apr 18, 2014 at 02:35:53PM -0700, Greg KH wrote:
> On Fri, Apr 18, 2014 at 06:30:44PM -0300, Aldo Esteban Paz wrote:
> > For the Eudyptula's Chanllenge Task 6, i need to write a misc device
> > driver with simple read/write operations.
> >  The following was the answer to part of my code:
> > 
> > > static char eid[] = EUDYPTULAID;
> > >
> > > static ssize_t misc_device_read(struct file *file, char __user *buf,
> > >                                         size_t count, loff_t *ppos)
> > > {
> > >         if (*ppos == sizeof(eid))
> > >                 return 0;
> > >         else
> > >                 if (*ppos != 0 || count < sizeof(eid))
> > >                         return -EINVAL;
> > >
> > >         if (copy_to_user(buf, eid, sizeof(eid)))
> > >                 return -EINVAL;
> > >
> > >         *ppos = sizeof(eid);
> > >
> > >         return *ppos;
> > > }
> > 
> > This whole function can be made much more "simple" and reduced to one
> > single line {hint} (It's just a "simple" function call {hint}).
> > 
> > Anyone know that "single" function?
> 
> Yes, but you really should do your own research for stuff like this,
> that's what the challenge is all about, not asking others to do it for
> you :(

I'm curious about this. I didn't get the simple, one-line function call feedback and
my task was accepted with a regular function definition, similar to the one from the
OP.

-- 
L. Alberto Gim?nez
GnuPG key ID 0xDD4E27AB

Simple Read operation on a misc device driver

[Fernando Apesteguía]

El 19/04/2014 18:52, "L. Alberto Gim?nez" <agimenez@sysvalve.es> escribi?:
>
> On Fri, Apr 18, 2014 at 02:35:53PM -0700, Greg KH wrote:
> > On Fri, Apr 18, 2014 at 06:30:44PM -0300, Aldo Esteban Paz wrote:
> > > For the Eudyptula's Chanllenge Task 6, i need to write a misc device
> > > driver with simple read/write operations.
> > >  The following was the answer to part of my code:
> > >
> > > > static char eid[] = EUDYPTULAID;
> > > >
> > > > static ssize_t misc_device_read(struct file *file, char __user *buf,
> > > >                                         size_t count, loff_t *ppos)
> > > > {
> > > >         if (*ppos == sizeof(eid))
> > > >                 return 0;
> > > >         else
> > > >                 if (*ppos != 0 || count < sizeof(eid))
> > > >                         return -EINVAL;
> > > >
> > > >         if (copy_to_user(buf, eid, sizeof(eid)))
> > > >                 return -EINVAL;
> > > >
> > > >         *ppos = sizeof(eid);
> > > >
> > > >         return *ppos;
> > > > }
> > >
> > > This whole function can be made much more "simple" and reduced to one
> > > single line {hint} (It's just a "simple" function call {hint}).
> > >
> > > Anyone know that "single" function?
> >
> > Yes, but you really should do your own research for stuff like this,
> > that's what the challenge is all about, not asking others to do it for
> > you :(
>
> I'm curious about this. I didn't get the simple, one-line function call
feedback and
> my task was accepted with a regular function definition, similar to the
one from the
> OP.

That feedback may come in the next tasks ;)

>
> --
> L. Alberto Gim?nez
> GnuPG key ID 0xDD4E27AB
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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