Hi Stephen, On Mon, 2016-10-31 at 11:06 -0700, Stephen Boyd wrote: > On 10/31, James Liao wrote: > > On Thu, 2016-10-27 at 18:17 -0700, Stephen Boyd wrote: > > > On 10/21, Erin Lo wrote: > > > > @@ -244,3 +256,31 @@ void mtk_clk_register_composites(const struct mtk_composite *mcs, > > > > clk_data->clks[mc->id] = clk; > > > > } > > > > } > > > > + > > > > +void mtk_clk_register_dividers(const struct mtk_clk_divider *mcds, > > > > + int num, void __iomem *base, spinlock_t *lock, > > > > + struct clk_onecell_data *clk_data) > > > > +{ > > > > + struct clk *clk; > > > > + int i; > > > > + > > > > + for (i = 0; i < num; i++) { > > > > + const struct mtk_clk_divider *mcd = &mcds[i]; > > > > + > > > > + if (clk_data && !IS_ERR_OR_NULL(clk_data->clks[mcd->id])) > > > > > > NULL is a valid clk. IS_ERR_OR_NULL is usually wrong. > > > > Why NULL is a valid clk? > > Perhaps at some point we'll want to return a NULL pointer to > clk_get() callers so that they can handle things like optional > clocks easily without having any storage requirements. I don't > know if we'll ever do that, but that's just a possibility. > > > > > clk_data is designed for multiple initialization from different clock > > types, such as infra_clk_data in clk-mt2701.c. So it will ignore valid > > clocks to avoid duplicated clock registration. Here I assume a clock > > pointer with error code or NULL to be an invalid (not initialized) > > clock. > > > > Ok. Would it be possible to initialize the array with all error > pointers? That would make things less error prone, but it Yes. Current mtk_alloc_clk_data() implementation init all elements with ERR_PTR(-ENOENT). > probably doesn't matter at all anyway because this is done during > registration time. IS_ERR_OR_NULL makes me take a second look > each time, because it's usually wrong. I see. Although currently all Mediatek clk drivers use mtk_alloc_clk_data() to allocate clk_data, I would like to keep the flexibility to support zero-initialized clk_data such as a static structure. So I prefer to treat a NULL pointer as an uninitialized clock. Best regards, James -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html