From: jassisinghbrar@xxxxxxxxx
Date: Thu, 30 Nov 2017 21:43:16 +0530
> + priv->eeprom_base = devm_memremap(&pdev->dev, eeprom_res->start,
> + resource_size(eeprom_res),
> + MEMREMAP_WT);
> + if (!priv->eeprom_base) {
> + dev_err(&pdev->dev, "devm_memremap() failed for EEPROM\n");
> + ret = -ENXIO;
> + goto free_ndev;
> + }
dev_memremap() is implemented via memremap() which for MEMREMAP_WT is
in turn implemented using ioremap_wt() which returns an "__iomem"
pointer.
The memremap() function talks about __iomem being about side effects.
That's not really the full story. The __iomem annotation is also
about whether a special accessor is necessary to "dereference" the
pointer. On sparc64, for example, the ioremap_*() functions return a
physical address not a virtual one. So you cannot directly
dereference pointers that are returned from the ioremap*() interfaces.
You'll also need to mark priv->eeprom_base as "__iomem".
devm_memremap() returns a straight "void *" without the __iomem
annotation, and this is wrong then ioremap_*() is used.
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