diff --git a/src/linear.jl b/src/linear.jl
index 0278ebe..071dc45 100644
--- a/src/linear.jl
+++ b/src/linear.jl
@@ -33,65 +33,64 @@ out, st = l(x, ps, st)
 println(out == x * transpose(W))) # true
 ```
 """
-struct LinearLayer{FEATFIRST} <: AbstractExplicitLayer
+struct LinearLayer{FEATFIRST} <: AbstractP4MLLayer
    in_dim::Integer
    out_dim::Integer
-   use_cache::Bool
    @reqfields()
 end
 
-LinearLayer(in_dim::Int, out_dim::Int; feature_first = false, use_cache = true) = LinearLayer{feature_first}(in_dim, out_dim, use_cache, _make_reqfields()...)
+LinearLayer(in_dim::Int, out_dim::Int; feature_first = false) = LinearLayer{feature_first}(in_dim, out_dim, _make_reqfields()...)
 
-_valtype(l::LinearLayer, x::AbstractArray, ps)  = 
-      promote_type(eltype(x), eltype(ps.W))
+# ----------------------- evaluation and allocation interfaces 
 
-function (l::LinearLayer)(x::AbstractVector, ps, st)
-   out = acquire!(st.pool, :A, (l.out_dim, ), _valtype(l, x, ps))
-   mul!(unwrap(out), ps.W, unwrap(x)); release!(x); 
-   return out, st
+_valtype(l::LinearLayer, x::AbstractArray, ps, st)  = promote_type(eltype(x), eltype(ps.W))
+_gradtype(l::LinearLayer, x, ps, st) = promote_type(eltype(x), eltype(ps.W))
+
+_out_size(l::LinearLayer, x::AbstractVector, ps, st) = (l.out_dim, )
+_out_size(l::LinearLayer{true}, x::AbstractMatrix, ps, st) = (l.out_dim, size(x, 2))
+_out_size(l::LinearLayer{false}, x::AbstractMatrix, ps, st) = (size(x, 1), l.out_dim)
+
+LuxCore.initialparameters(rng::AbstractRNG, l::LinearLayer) = ( W = randn(rng, l.out_dim, l.in_dim), )
+LuxCore.initialstates(rng::AbstractRNG, l::LinearLayer) = NamedTuple()
+
+function whatalloc(::typeof(evaluate!), l::LinearLayer, x::AbstractArray, ps, st)
+   TV = _valtype(l, x, ps, st)
+   sz = _out_size(l, x, ps, st)
+   return (TV, sz...)
 end
 
-function (l::LinearLayer{true})(x::AbstractMatrix, ps, st)
-   out = acquire!(st.pool, :bA, (l.out_dim, size(x, 2)), _valtype(l, x, ps)); 
-   mul!(unwrap(out), ps.W, unwrap(x)); release!(x); 
+function evaluate!(out, l::LinearLayer, x::AbstractVecOrMat, ps, st)
+   mul!(out, ps.W, x)
    return out, st
 end
 
-(l::LinearLayer{false})(x::AbstractMatrix, ps, st) = begin
-   out = acquire!(st.pool, :bA, (size(x, 1), l.out_dim), _valtype(l, x, ps)); 
-   mul!(unwrap(out), unwrap(x), transpose(PtrArray(ps.W))); release!(x);
+function evaluate!(out, l::LinearLayer{false}, x::AbstractMatrix, ps, st)
+   mul!(out, x, transpose(PtrArray(ps.W)))
    return out, st
 end
- 
-# Jerry: Maybe we should use Glorot Uniform if we have no idea about what we should use?
-LuxCore.initialparameters(rng::AbstractRNG, l::LinearLayer) = 
-      ( W = randn(rng, l.out_dim, l.in_dim), )
-
-LuxCore.initialstates(rng::AbstractRNG, l::LinearLayer) = 
-      ( l.use_cache ?  (pool =  ArrayPool(FlexArrayCache), ) 
-                    : (pool =  ArrayPool(FlexArray), ))
- 
+
+# --------------------- connect with ChainRules 
+# can this be generalized again? 
 # TODO: check whether we can do this without multiple dispatch on vec/mat without loss of performance
-function rrule(::typeof(LuxCore.apply), l::LinearLayer, x::AbstractVector, ps, st)
-   val = l(x, ps, st)
-   function pb(A)
-      return NoTangent(), NoTangent(), ps.W' * A[1], (W = A[1] * x',), NoTangent()
-   end
-   return val, pb
-end
 
-function rrule(::typeof(LuxCore.apply), l::LinearLayer, x::AbstractMatrix, ps, st)
+import ChainRulesCore: rrule, NoTangent
+
+function rrule(::typeof(evaluate), l::LinearLayer, x::AbstractVecOrMat, ps, st)
    val = l(x, ps, st)
+
    function pb(A)
       return NoTangent(), NoTangent(), ps.W' * A[1], (W = A[1] * x',), NoTangent()
    end
+
    return val, pb
 end
 
-function rrule(::typeof(LuxCore.apply), l::LinearLayer{false}, x::AbstractMatrix, ps, st)
+function rrule(::typeof(evaluate), l::LinearLayer{false}, x::AbstractMatrix, ps, st)
    val = l(x, ps, st)
+
    function pb(A)
-      return NoTangent(), NoTangent(), A[1] * ps.W, (W = transpose(PtrArray(A[1])) * unwrap(x),), NoTangent()
+      return NoTangent(), NoTangent(), A[1] * ps.W, (W = transpose(PtrArray(A[1])) * x,), NoTangent()
    end
+
    return val, pb
 end
\ No newline at end of file
diff --git a/test/runtests.jl b/test/runtests.jl
index f10ac63..be33f4a 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -22,7 +22,7 @@ using Test
     @testset "Sparse Symmetric Product" begin include("ace/test_sparsesymmprod.jl"); end 
     @testset "Sparse Symmetric Product - DAG" begin include("ace/test_sparsesymmproddag.jl"); end 
     @testset "Sparse Product" begin include("test_sparseproduct.jl"); end 
-    # @testset "Linear layer" begin include("test_linear.jl"); end 
+    @testset "Linear layer" begin include("test_linear.jl"); end 
     
     # Misc
     @testset "Static Prod" begin include("test_staticprod.jl"); end