Access_Qualifiers(3) Access Qualifiers for image memory objects.

__read_only __write_only read_only write_only


Image objects specified as arguments to a kernel can be declared to be read-only or write-only. A kernel cannot read from and write to the same image object. The __read_only (or read_only) and __write_only (or write_only) qualifiers must be used with image object arguments to declare if the image object is being read or written by a kernel. The default qualifier is __read_only.


The __read_only, __write_only, __read_write, read_only, write_only and read_write names are reserved for use as access qualifiers and shall not be used otherwise.


In the example below, imageA is a read-only 2D image object, and imageB is a write-only 2D image object.

__kernel void foo (read_only image2d_t imageA, write_only image2d_t imageB) { ... }


m[blue]OpenCL Specificationm[][1]


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OpenCL Specification
page 226, section 6.6 - Access Qualifiers