>Hi, Scott, Greg,
>
>Thank you for your helpful comments.
>For that Greg mentioned that the patch (or patch series) via UIO should worked
>through,
>so I want to make it clear that if it would go upstream?(And if so, when? No
>push, just ask)
>
>Also I have been wondering how the patches with components in different
>subsystems
>go get upstream to the mainline? Like patch 1-3 are of linuxppc-dev, and patch
>4 is of
>subsystem UIO, and if acceptable, how would you deal with them?
>
>Back to the devicetree thing, I make it detached from hardware compatibilities
>which belong
>to the hardware level driver and also used module parameter for of_id
>definition as dt-binding
>is not allowed for UIO now. So as I can see, things may go well and there is
>no harm to anything,
>I hope you(Scott) please take a re-consideration.
>
I mean I have get some new work done based on the comments of Arnd, Scott and
Greg. Also a lot of tests done.
So it would be better to make it clear whether I shoud keep the work going or
the UIO version is to be accepted
to go upstream recently in the future.
Thanks & regards,
Wenhu
>
>>On Sun, 2020-04-19 at 20:05 -0700, Wang Wenhu wrote:
>>> +static void sram_uapi_res_insert(struct sram_uapi *uapi,
>>> + struct sram_resource *res)
>>> +{
>>> + struct sram_resource *cur, *tmp;
>>> + struct list_head *head = &uapi->res_list;
>>> +
>>> + list_for_each_entry_safe(cur, tmp, head, list) {
>>> + if (&tmp->list != head &&
>>> + (cur->info.offset + cur->info.size + res->info.size <=
>>> + tmp->info.offset)) {
>>> + res->info.offset = cur->info.offset + cur->info.size;
>>> + res->parent = uapi;
>>> + list_add(&res->list, &cur->list);
>>> + return;
>>> + }
>>> + }
>>
>>We don't need yet another open coded allocator. If you really need to do this
>>then use include/linux/genalloc.h, but maybe keep it simple and just have one
>>allocaton per file descriptor so you don't need to manage fd offsets?
>>
>>> +static struct sram_resource *sram_uapi_find_res(struct sram_uapi *uapi,
>>> + __u32 offset)
>>> +{
>>> + struct sram_resource *res;
>>> +
>>> + list_for_each_entry(res, &uapi->res_list, list) {
>>> + if (res->info.offset == offset)
>>> + return res;
>>> + }
>>> +
>>> + return NULL;
>>> +}
>>
>>What if the allocation is more than one page, and the user mmaps starting
>>somewhere other than the first page?
>>
>>> + switch (cmd) {
>>> + case SRAM_UAPI_IOC_SET_SRAM_TYPE:
>>> + if (uapi->sa)
>>> + return -EEXIST;
>>> +
>>> + get_user(type, (const __u32 __user *)arg);
>>> + uapi->sa = get_sram_api_from_type(type);
>>> + if (uapi->sa)
>>> + ret = 0;
>>> + else
>>> + ret = -ENODEV;
>>> +
>>> + break;
>>> +
>>
>>Just expose one device per backing SRAM, especially if the user has any reason
>>to care about where the SRAM is coming from (correlating sysfs nodes is much
>>more expressive than some vague notion of "type").
>>
>>> + case SRAM_UAPI_IOC_ALLOC:
>>> + if (!uapi->sa)
>>> + return -EINVAL;
>>> +
>>> + res = kzalloc(sizeof(*res), GFP_KERNEL);
>>> + if (!res)
>>> + return -ENOMEM;
>>> +
>>> + size = copy_from_user((void *)&res->info,
>>> + (const void __user *)arg,
>>> + sizeof(res->info));
>>> + if (!PAGE_ALIGNED(res->info.size) || !res->info.size)
>>> + return -EINVAL;
>>
>>Missing EFAULT test (here and elsewhere), and res leaks on error.
>>
>>> +
>>> + res->virt = (void *)uapi->sa->sram_alloc(res->info.size,
>>> + &res->phys,
>>> + PAGE_SIZE);
>>
>>Do we really need multiple allocators, or could the backend be limited to just
>>adding regions to a generic allocator (with that allocator also serving in-
>>kernel users)?
>>
>>If sram_alloc is supposed to return a virtual address, why isn't that the
>>return type?
>>
>>> + if (!res->virt) {
>>> + kfree(res);
>>> + return -ENOMEM;
>>> + }
>>
>>ENOSPC might be more appropriate, as this isn't general-purpose RAM.
>>
>>> +
>>> + sram_uapi_res_insert(uapi, res);
>>> + size = copy_to_user((void __user *)arg,
>>> + (const void *)&res->info,
>>> + sizeof(res->info));
>>> +
>>> + ret = 0;
>>> + break;
>>> +
>>> + case SRAM_UAPI_IOC_FREE:
>>> + if (!uapi->sa)
>>> + return -EINVAL;
>>> +
>>> + size = copy_from_user((void *)&info, (const void __user *)arg,
>>> + sizeof(info));
>>> +
>>> + res = sram_uapi_res_delete(uapi, &info);
>>> + if (!res) {
>>> + pr_err("error no sram resource found\n");
>>> + return -EINVAL;
>>> + }
>>> +
>>> + uapi->sa->sram_free(res->virt);
>>> + kfree(res);
>>> +
>>> + ret = 0;
>>> + break;
>>
>>So you can just delete any arbitrary offset, even if you weren't the one that
>>allocated it? Even if this isn't meant for unprivileged use it seems error-
>>prone.
>>
>>> +
>>> + default:
>>> + pr_err("error no cmd not supported\n");
>>> + break;
>>> + }
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static int sram_uapi_mmap(struct file *filp, struct vm_area_struct *vma)
>>> +{
>>> + struct sram_uapi *uapi = filp->private_data;
>>> + struct sram_resource *res;
>>> +
>>> + res = sram_uapi_find_res(uapi, vma->vm_pgoff);
>>> + if (!res)
>>> + return -EINVAL;
>>> +
>>> + if (vma->vm_end - vma->vm_start > res->info.size)
>>> + return -EINVAL;
>>> +
>>> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>>> +
>>> + return remap_pfn_range(vma, vma->vm_start,
>>> + res->phys >> PAGE_SHIFT,
>>> + vma->vm_end - vma->vm_start,
>>> + vma->vm_page_prot);
>>> +}
>>
>>Will noncached always be what's wanted here?
>>
>>-Scott
>>
>>
>
>
