Messages in this thread | | | Date | Fri, 11 Apr 2008 12:41:54 +0200 | From | Uwe Kleine-König <> | Subject | Re: [PATCH 4/4] [RFC] UIO: generic platform driver |
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Hello Hans,
Hans J. Koch wrote: > On Fri, Apr 11, 2008 at 08:21:06AM +0200, Uwe Kleine-König wrote: > > > > + for (i = 0; i < pdev->num_resources; ++i) { > > > > + struct resource *r = &pdev->resource[i]; > > > > > > Please don't define new variables in the middle of a function. > > This is a matter of taste. In my eyes it's better to declare it here > > because then it's easier to see where it's used. > > No. It's more important to see which variables are declared in the > function and which are declared elsewhere. If you have to search the > whole body of a function for possible declarations, this is BAD. And if > it's not clear where a variable is used, the function is too long or has > other style problems. Your function is short and clean, so where's the > problem? Please move the declaration to the top of the function. I'm not conviced and still prefer it that way. I gave way for your requests in uio.c because it's your code. I want to leave it as it is and hope you will accept that (as this is my code).
> > BTW would you be open to redefine uio_info as: > > > > struct uio_info { > > struct uio_device *uio_dev; > > ... > > size_t num_memmaps; > > struct uio_mem mem[]; > > } > > > > This allows to allocate exactly the number of members in the mem array > > that are needed (for the cost of a size_t). (You just do: > > > > uio_info uioinfo = kzalloc(sizeof(*uioinfo) + num_memmaps * sizeof(uioinfo->mem[0]), GFP_KERNEL); > > > > it's still one chunk of memory and usage is similar---just with > > MAX_UIO_MAPS substituted by uioinfo->num_memmaps.) > > I don't like it. It makes things more complicated without any obvious > gain. Most use cases I imagine only use a single mapping, so the gain would be to save 4 (or later more) 'struct uio_mem's per device.
> sizeof(struct uio_info) would return wrong values, For which definition of wrong? sizeof(struct uio_info) don't include space for mem then, but in my eyes that's correct. Having to care about the size of mem is the burden when it's not constant.
> you need to > free the extra memory, There is no extra memory because uioinfo and it's mem member are allocated together with a single kzalloc (and must be). (Thats the difference to
struct uio_info { ... size_t num_memmaps; struct uio_mem *mem; };
.) > userspace applications need to be able to deal > with 10000 mappings... For the userspace it's exactly the same, isn't it?
Best regards Uwe
-- Uwe Kleine-König, Software Engineer Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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