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.
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
>
>
