linux-kernel - Re: [PATCH v12 5/7] nvmem: core: Rework layouts to become regular devices

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 11 Oct 2023 12:58:59 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Walle <michael@...le.cc>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Robert Marko <robert.marko@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Randy Dunlap <rdunlap@...radead.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Daniel Golle <daniel@...rotopia.org>
Subject: Re: [PATCH v12 5/7] nvmem: core: Rework layouts to become regular
 devices

Hi Srinivas,

> > you don't have access to your modules. And anyway it's probably a bad
> > idea to allow endless probe deferrals on your main storage device.
> > 
> > If the cells are not available at that time, it's not a huge deal? The
> > consumers will have to wait a bit more (or take any other action, this
> > is device dependent).  
> 
> In this case the nvmem consumers will get an -ENOENT error, which is very confusing TBH.

Maybe we can solve that situation like that (based on my current
series):

--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1448,7 +1448,10 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np, const char *id)
        of_node_put(cell_np);
        if (!cell_entry) {
                __nvmem_device_put(nvmem);
-               return ERR_PTR(-ENOENT);
+               if (nvmem->layout)
+                       return ERR_PTR(-EAGAIN);
+               else
+                       return ERR_PTR(-ENOENT);
        }
 
        cell = nvmem_create_cell(cell_entry, id, cell_index);


So this way when a (DT) consumer requests a cell:
- the cell is ready and it gets it
- the cell is not ready and...
   - the cell comes from a layout -> we return EAGAIN, which
     means the cell is not yet ready and this must be retried later
     (the caller may return EPROBE_DEFER in this case).
   - the cell is simply missing/not existing/not available, this is a
     real error.

What do you think?

Thanks,
Miquèl