Messages in this thread | | | Date | Thu, 31 Aug 2023 11:11:40 -0700 | From | Dan Williams <> | Subject | RE: [PATCH v9 02/15] cxl/regs: Prepare for multiple users of register mappings |
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Terry Bowman wrote: > From: Robert Richter <rrichter@amd.com> > > The function devm_cxl_iomap_block() is used to map register mappings > of CXL component or device registers. A @dev is used to unmap the IO > regions during device removal. > > Now, there are multiple devices using the register mappings. E.g. the > RAS cap of the Component Registers is used by cxl_pci, the HDM cap > used in cxl_mem. This could cause IO blocks not being freed and a > subsequent reinitialization to fail if the same device is used for > both. > > To prevent that, expand cxl_map_component_regs() to pass a @dev to be > used with devm to IO unmap. This allows to pass the device that > actually is creating and using the IO region. > > For symmetry also change the function i/f of cxl_map_device_regs().
I think @dev is too ambiguous as a name. I.e. when does @dev refer to the 'struct device *' instance that the registers belong, and when does @dev refer to the 'struct device *' instance hosting the mapping for devm operations?
One of the ways I have tried to disambiguate that distinction is using the name @host to explicitly refer to the context of devm operations, and @dev is only for context for dev_dbg() operations. Can you clarify this patch by using @host everywhere that the devm context is being handled?
This would also satisfy Jonathan's concern. I think it needs to be the case that @map is explicit about when it is conveying some @dev context for dev_dbg() messages and when it is conveying the @host for devm operations because those are 2 different concepts.
It looks like @dev argument you are plumbing here is for when @map->dev cannot be used for devm operations, so at a minimum use @host as the variable name to make that clear...
...or always make it the case that @map carries an @host parameter which would mean that ports would need their own copy of the comp_map versus directly reusing the one in the cxlds since those 2 mapping instances need different @host parameters. That feels cleaner to me then "sometimes map->dev can be used for devm and sometimes not". @map->host is always the devm context.
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